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  • 1.
    Pamidi, Taraka Rama Krishna
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Process Intensification by Ultrasound Controlled Cavitation2019Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Process industries are cornerstones in today’s industrialized society. They contribute significantly in the manufacturing of various goods and products that are used in our day-to-day life. Our society’s paradigm of consumerism accompanied by a rise in global population drives an ever increasing demand for goods. One of many strategies developed to satisfy these demands and at the same time improve production capabilities is known as process intensification. As an example, this can be accomplished by implementation of devices using the principle of hydrodynamic and acoustic cavitation. High-intensity cavitation in the ultrasonic range can change the physical and chemical properties of a wide range of substances and hence, improve the production rate or quality.

    Despite the generally accepted benefits of hydrodynamic and acoustic cavitation, applications in the process industry are yet limited. The reasons are that the method requires extensive optimization, which depends on multiple process parameters and encounters problem in the implementation on a larger scale. Scalable cavitation reactor concepts for industrial applications need to meet challenges like stability and robustness, energy efficiency and high flow rates. This thesis focuses on the methodology for the design and optimization of a flow through cavitation reactor.

    An ultrasound reactor concept has been developed and tested for two different applications: i) Fibrillation processes typical for paper and pulp industry; ii) Metal leaching of mineral concentrates. Simulations were carried out using a commercially available software for multiphysics modeling which combines acoustics, structural dynamics, fluid dynamics and piezoelectrics. However, the optimization procedure requires extensive experimental work in parallel with multi-physical simulations. In general, the application leads to hydrodynamic initiation of small gas bubbles in the fluid to be excited and collapsed by high-intensity ultrasound. This transient collapse of the cavitation bubbles provides both mechanical and chemical effect on materials.

    The developed reactor has a power conversion efficiency of 36% in batch mode and is well suited for a scale-up. In flow-through mode, the cavitation effect improves extensively and provides stable results. Energy efficiency requires hydrodynamic initiation of cavitation bubbles, high acoustic cavitation intensity by multiple excitation frequencies adapted to the optimized reactor geometry, as well as optimal process pressure and temperature with respect to the materials to be treated. The impact of flow conditions and hydrodynamic cavitation is significant and almost doubles the yield at the same ultrasonic power input.

    In the case of fibrillation of cellulose fibers, results obtained indicate that generated cavitation intensity changes the mechanical properties of the fiber wall. In the case of leaching, experiments show that six hours of exposure gave a 57% recovery of tungsten from the scheelite concentrate at 80°C and atmospheric pressure. Future research will focus on different types of excitation signals, extended reactor volume, increased flow rates and use of a higher process temperature. 

  • 2.
    Ljunggren, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Simmons, Christian
    Simmons akustik och utveckling, Chalmers Teknikpark, Gothenburg, Sweden.
    Airborne sound insulation between dwellings, from 50 vs. 100 Hz: a compilation of Swedish field surveys2018Ingår i: Applied Acoustics, ISSN 0003-682x, Vol. 133, s. 58-63Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It has for long been debated whether 50 or 100 Hz is the proper lower frequency limit when evaluating airborne sound insulation between dwellings. Although 100 Hz is the lowest third-octave band within most regulations, there is an ongoing interest in paying more attention to lower frequencies. In Sweden, evaluation from 50 Hz became mandatory already in 1999 wherefore unique experiences are available by now. In this paper, extensive data in terms of field measurements and questionnaire surveys from in total 46 building objects of various constructions have been compiled. A number of single number quantities, standardized by ISO as well as alternatives, are compared concerning their correlation against the subjectively rated annoyance responded by the residents. The statistical evidence for a 50 Hz limit was found to be small considering the total database but when the lightweight buildings were analyzed by their own, the importance of frequencies below 100 Hz became clearer. The overall recommendation is to include frequencies from 50 Hz in order to achieve good sound protection against a broad variety of sound sources, including music and other possible items generating low frequencies.

  • 3.
    Pamidi, Taraka Rama Krishna
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johansson, Örjan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Comparison of Different Concepts of UltrasoundReactors Using Numerical Simulations2018Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Sonochemical reactors are used for process intensification based on efficientenergy transfer due to ultrasound in order to cause transient cavitation in the medium.Ultrasonic reactors are extensively used for numerous applications due to their differentfeatures. The process of ultrasound cavitation can be defined as generation, growth andviolent collapse of microbubbles under ultrasonic irradiation which can release a highamount of energy in a small volume. The released energy causes a sudden increase intemperature and pressure which thereby can lead to extensive process intensification. Thepresent work deals with the evaluation of two different configurations of ultrasound reactorsusing both numerical modeling and experimental verification. The evaluation is based onprediction of the pressure distribution, verified by foil tests and with calorimetric method.The two reactors were developed to be used for the treatment of cellulose fibers to improveenergy efficiency in the fibrillation process. The goal is to optimize cavitation intensityand minimize the coupling loss factors. The development and evaluation of these two reactorconcepts aim to improve the design methodology for a scalable flow through reactor conceptwith high yield and energy efficiency

  • 4.
    Shankar, Vijay
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Bengston, Andreas
    Chalmers University of Technology.
    Fransson, Victor
    Chalmers University of Technology.
    Hagentoft, Carl-Eric
    Chalmers University of Technology.
    Numerical analysis of the influence of natural convection in attics: A CFD analysis2018Ingår i: / [ed] T E Simos; Ch Tsitouras;, American Institute of Physics (AIP), 2018, artikel-id 470010Konferensbidrag (Refereegranskat)
    Abstract [en]

    As the design of the building envelope has changed, the parameters that govern thermal insulation, air tightness and the complex heat transfer processes are often neglected. This aim of this research work is to numerically investigate the influence of natural convection in attics with joists and insulation. With the help of Computational Fluid Dynamics (CFD), more specifically the software ANSYS Fluent, 3D simulations are conducted for both porous layer and air cavity to estimate the magnitude of heat transfer. The same was executed for porous media with two different values of permeability. A suitable turbulence model has been applied to account for the highly sensitive buoyancy driven flow. The results are presented in form of dimensionless numbers, Nusselt number versus modified Rayleigh number. It can be concluded that the temperature difference and permeability play a vital role.

  • 5.
    Lindegren, David
    et al.
    Ericsson Research, Sweden.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Ljung, Robert
    Engineering psychology, University of Gävle.
    The AMR-NB Voice Codec Reduces the Listener’s Capacity to Recall Speech2018Ingår i: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 104, nr 3, s. 381-384Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Modern telecommunication services generally use digital speech encoding. Speech encoding degrades the audio with compression and filters to make the data transmission more efficient. To keep conversations and on-line meetings productive and creative it is important that these digital services do not increase the cognitive load. Measuring effects on working memory is one way to estimate cognitive load of the listener. A test with 25 participants was performed to investigate the effects of using the AMR-NB codec, a standardized codec for mobile communication. The memory performance for spoken 12-word lists was measured and AMR-NB encoded speech was compared with unprocessed speech (LPCM 16 bit, 44.1 kHz). A within-subject analysis showed 9% lower recall rate for the AMR-NB coded speech.

  • 6.
    Shankar, Vijay
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Hellsvik, Ragnar
    Chalmers University of Technology.
    Hagentoft, Carl-Eric
    Chalmers University of Technology.
    Transient heat transfer and moisture load in cold attic constructions: A CFD analysis2018Ingår i: / [ed] T E Simos; Ch Tsitouras;, American Institute of Physics (AIP), 2018, artikel-id 470011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Mold growth in cold attic constructions has become an increasing problem in Sweden and other countries with cold climates due to the demands on energy efficient building envelopes. Highly insulated building envelopes with cold ventilated attics lead to colder climates in the attic space, which increases the risk for mold growth. In this paper, the transient heat transfer process including natural and forced convection is investigated for a 24-hour cycle in a virtual 3D model of a ventilated attic construction by the use of CFD technology. The momentum and energy equations along with the realizable k-epsilon turbulence model are solved with commercial CFD software. Transient simulations are performed for daily temperature variations for various ventilation rates and a hygrothermal analysis is conducted to estimate the risk for mold growth at the inner roof boundary. A virtual model of a ventilated attic with an underlying layer of porous medium is used for the simulations and the CFD approach is based on a validated model from previous research. The results are the temperature field and the risk for mold growth for different ventilation rates presented as a function of time during the cycle.

  • 7.
    Öqvist, Rikard
    et al.
    Tyréns AB, Umeå, Sweden.
    Ljunggren, Fredrik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Variations in sound insulation from 20 Hz in lightweight dwellings2018Ingår i: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 66, nr 1, s. 56-65Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of this study is to quantify the total variations in impact and airborne sound insulation from 20 and 50 Hz, respectively, within a wood-based building system. Field measurements in 70 rooms have been statistically analyzed, in weighted metrics and in third octave bands. Since 1994, the Swedish building code permits wood-based high-rise multifamily dwellings. However, the low frequency sound insulation soon turned out to be insufficient, and complaints were more common in lightweight buildings compared to traditional heavy constructions. Therefore, in 1999, the extended frequency range 50–3150 Hz was introduced in the requirements, an action that mitigated the problem, but only to some extent. Consequently, the lightweight industry often aims one sound class (4 dB) higher than the minimum requirements to obtain satisfactory performance. The Swedish research program Aku20 (2014–2017) showed that the correlation between measured and perceived impact sound insulation in lightweight constructions was significantly improved, when even lower frequencies (20–50 Hz) were included. In this context, the variations of low frequency field measurements and corresponding safety margins need to be investigated.

  • 8.
    Öqvist, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik. Tyréns AB.
    Ljunggren, Fredrik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Walking sound annoyance vs. impact sound insulation from 20 Hz2018Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 135, s. 1-7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is a need to develop single number quantities (SNQ) of impact sound insulation that correlate better with walking sound annoyance. Previous research has indicated that impact sound insulation should be evaluated from 20 Hz in lightweight constructions, using modified spectrum adaptation terms. The purpose of our study was to verify whether frequencies between 20 and 50 Hz are important for perceived walking sound annoyance and to verify whether the proposed spectrum adaptation terms improve correlation with perceived walking sound annoyance. Binaural recordings of walking sound in one heavy and one lightweight construction were evaluated in a two-part listening test. The need to include frequencies from 20 Hz when evaluating lightweight constructions was verified. Both tested constructions achieved similar performance in terms of LnT,w and LnT,w + CI,50-2500, while a significant mismatch in the rated annoyance was observed. The correlation between SNQ and subjective response was considerably improved, when the impact sound insulation was evaluated from 20 or 25 Hz using a flat frequency-weighting factor.

  • 9.
    Lundkvist, André
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Stridfelt, Jakob
    Luleå tekniska universitet.
    3D Auditory Displays for Parking Assistance Systems2017Ingår i: SAE International Journal of Passenger Cars - Electronic and Electrical Systems, ISSN 1946-4614, E-ISSN 1946-4622, Vol. 10, nr 1, s. 17-23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of this study was to investigate if 3D auditory displays could be used to enhance parking assistance systems (PAS). Objective measurements and estimations of workload were used to assess the benefits of different 3D auditory displays. In today’s cars, PAS normally use a visual display together with simple sound signals to inform drivers of obstacles in close proximity. These systems rely heavily on the visual display, as the sound does not provide information about obstacles' location. This may cause the driver to lose focus on the surroundings and reduce situational awareness. Two user studies (during summer and winter) were conducted to compare three different systems. The baseline system corresponded to a system normally found in today’s cars. The other systems were designed with a 3D auditory display, conveying information of where obstacles were located through sound. A visual display was also available. Both normal parking and parallel parking was conducted. Time taken for parking and the number of obstacles/curb hits were recorded. Participants answered a NASA TLX questionnaire after evaluating each PAS for estimation of their experienced workload. Most participants enjoyed the additional information provided by the 3D auditory displays. The winter trial showed a significant reduction in perceived effort when using a 3D auditory display compared to the baseline. The summer trial showed tendencies of higher mental demand and frustration with the baseline compared to the 3D auditory displays. The results suggest that 3D auditory displays can be appreciated and useful in difficult parking situations.

  • 10.
    Ljunggren, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Simmons, Christian
    Simmons akustik och utveckling.
    Öqvist, Rikard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Correlation between sound insulation and occupants’ perception: Proposal of alternative single number rating of impact sound, part II2017Ingår i: Applied Acoustics, ISSN 0003-682x, Vol. 123, s. 143-151Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A previous Swedish research project indicated the potential need for evaluating impact sound insulation from 20 Hz in buildings with lightweight constructions. This is a discrepancy compared to the commonly used frequency intervals starting from 50 or 100 Hz. The statistical significance of this groundbreaking suggestion was however not satisfactorily strong since the result was based upon a limited number of building objects.

    The scope of the present paper is to secure the previous study by adding additional objects to the underlying database, thereby increasing the confidence of the results. The methodology is to perform impact sound insulation measurements in apartment buildings of various construction types and to perform questionnaire surveys among the residents. The measured sound insulation is compared to the subjective rating by the occupants in order to find the parameter giving the highest correlation with respect to frequency range and weighting.

    The highest correlation was found when the impact sound insulation was evaluated from 25 Hz using a flat frequency-weighting factor. Frequencies below 50 Hz are of great importance when evaluating impact sound insulation in lightweight constructions

  • 11.
    Johansson, Örjan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Pamidi, Taraka Rama Krishna
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Design of a high-intensity ultrasound reactor2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Design, and optimization of ultrasonic reactors are important objectives in sonochemical processing. The recent expansion of the use of ultrasonic reactors in various research areas all faces the problem of scaling up from laboratory results to industrial purposes. A traditional ultrasonic reactor usually has several issues, such as low effectiveness as well as complex and unstable system performance, which all are unfavorable for efficient sonochemical processing. This study addresses these issues and investigates a new flow type ultrasonic reactor designed to generate transient cavitation as the main source for ultrasound. Some important factors like pressure, material, flow and geometry are considered in the design. Numerical optimization as well as experimental investigations are performed to reach an optimized, energy-efficient and controlled ultrasound cavitation reactor. Results from numerical modeling are used for acoustic optimization of the reactor, which is driven with three transducers mounted radially in the reactor wall with 120° spacing. The final reactor is excited with dual frequencies a total of 9 sonotrodes. The reactor is intended to be used in studies of pre-treatment of cellulose fibers aiming at developing an alternative, energy efficient fibrillation process and for ultrasound leaching of minerals.

  • 12.
    Johansson, Örjan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Pamidi, Taraka Rama Krishna
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Design of a high-intensity ultrasound reactor2017Ingår i: IEEE International Ultrasonics Symposium, IUS, Piscataway, NJ: IEEE Computer Society, 2017, artikel-id 8091660Konferensbidrag (Refereegranskat)
    Abstract [en]

    Design, and optimization of ultrasonic reactors are important objectives in sonochemical processing. The recent expansion of the use of ultrasonic reactors in various research areas all faces the problem of scaling up from laboratory results to industrial purposes. A traditional ultrasonic reactor usually has several issues, such as low effectiveness as well as complex and unstable system performance, which all are unfavorable for efficient sonochemical processing. This study addresses these issues and investigates a new flow type ultrasonic reactor designed to generate transient cavitation as the main source for ultrasound. Some important factors like pressure, material, flow and geometry are considered in the design. Numerical optimization as well as experimental investigations are performed to reach an optimized, energy-efficient and controlled ultrasound cavitation reactor. Results from numerical modeling are used for acoustic optimization of the reactor, which is driven with three transducers mounted radially in the reactor wall with 120° spacing. The final reactor is excited with dual frequencies a total of 9 sonotrodes. The reactor is intended to be used in studies of pre-treatment of cellulose fibers aiming at developing an alternative, energy efficient fibrillation process and for ultrasound leaching of minerals

  • 13.
    Johansson, Örjan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Pamidi, Taraka Rama Krishna
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Design of high-intensity ultrasound reactor2017Ingår i: IEEE International Ultrasonics Symposium, IUS, Piscataway, NJ: IEEE Computer Society, 2017, artikel-id 8092948Konferensbidrag (Refereegranskat)
    Abstract [en]

    Design and optmiziation of ultrasonic reactors are important objectives in sonochemical processing. The recent expansion of the use of ultrasonic reactors in various research projects all faces the problem of scaling up laboratory results for industrial use. A traditional ultrasonic reactor usually has several issues, such as low effectiveness and complex and unstable system performance, which all are unfavorable for efficient sonochemical processing. This study adresses these issues and investigates a new flow type ultrasonic reactor designed to generate transient cavitation as the main source for ultrasound for sonochemical processing. This study proposes the principle of the flow type ultrasonic reactor design to generate transient cavitation. The objective of this work is to design an ultrasonic reactor with a new geometry. The idea is to improve process efficiency based on resonance enhanced ultrasound controlled cavitation

  • 14.
    Nykänen, Arne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Löfdahl, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johannesson, Tomas
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Medier ljudteknik och upplevelseproduktion och teater.
    Berg, Jan
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Medier ljudteknik och upplevelseproduktion och teater.
    Do In-ear monitors protect musicians' hearing?2017Ingår i: 142nd Audio Engineering Society International Convention 2017, AES 2017, 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    In-ear monitors for live performances are commonly considered to give better sound quality than loudspeaker monitors. They are also often assumed to reduce sound exposure. Because of lack of evidence for this, sound exposure for pop/rock/jazz musicians was compared between performances with in-ear and loudspeaker monitors. Equivalent sound pressure levels at the musicians' ears were 94 to 105 dBA with loudspeaker and 86 to 108 dBA with in-ear monitors. Many participants used earplugs when using loudspeaker monitors. Therefore, the recommendation, from a pure hearing protection perspective, is to use loudspeaker monitors and earplugs. However, the large spread in levels between musicians using in-ear monitors suggests that with better training and measurements of sound exposure, in-ear monitors could be used safely.

  • 15.
    Ljunggren, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Simmons, Christian
    Simmons akustik och utveckling.
    Öqvist, Rikard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Evaluation of impact sound insulation from 20 Hz2017Ingår i: / [ed] Gibbs B., International Institute of Acoustics and Vibration , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to reduce costly downtime, adequate condition monitoring of the automatic transmission components in heavy duty construction equipment is necessary. The transmission in such equipment enables to change the gear ratio automatically. Further, the bearings in an automatic transmission provide low friction support to its rotating parts and act as an interface separating stationary from rotating components. Wear or other bearing faults may lead to an increase in energy consumption as well as failure of other related components in the automatic transmission, and thus costly downtime. In this study, different sensor data (particularly vibration) was collected on the automatic transmission during controlled test cycles in an automatic transmission test rig to enable adequate condition monitoring.

    An analysis of the measured vibration data was carried out using signal processing methods. The results indicate that predictive maintenance information related to the automatic transmission bearings may be extracted from vibrations measured on an automatic transmission. This information may be used for early fault detection, thus improving uptime and availability of heavy duty construction equipment.

  • 16.
    Berg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Medier ljudteknik och upplevelseproduktion och teater.
    Johannesson, Tomas
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Medier ljudteknik och upplevelseproduktion och teater.
    Löfdahl, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    In-ear vs. loudspeaker monitoring for live Sound and the effect on audio quality attributes and musical performance2017Ingår i: 142nd Audio Engineering Society International Convention 2017, AES 2017, 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    A successful performance of live music is dependent on how well musicians can hear themselves and the other members of the ensemble. Sound reinforcement systems can offer monitoring either by on-stage loudspeakers or in-ear headphones. These two monitoring conditions were compared to search for perceived auditory differences that affect parts of musical performance. Four jazz/pop/rock bands made live performances where monitor sound was provided to the musicians. Each band repeated their performance, changing from one monitoring condition to the other. After every performance, the musicians responded to questionnaires covering musical performance and audio quality. Experts also assessed recordings of the performances. Results show that perceived differences exist in audio quality and musical performance between loudspeaker monitors and in-ear headphone monitors.

  • 17.
    Öqvist, Rikard
    et al.
    Tyréns AB, Umeå.
    Ljunggren, Fredrik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Listening test of walking noise from 20 Hz in dwellings2017Ingår i: INTER-NOISE 2017: 46th International Congress and Exposition on Noise Control Engineering: Taming Noise and Moving Quiet, Institute of Noise Control Engineering , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Walking noise annoyance from the neighbor above tend to be higher in lightweight than in heavy constructions, even with exactly the same measured impact sound level. The Swedish research program AkuLite indicated that the correlation between measured impact sound insulation and annoyance was significantly improved by extending current ISO evaluation methods from 50 Hz down to 20 Hz. Consequently, there is a need to develop new metrics of impact sound insulation that better correspond to the perceived sound quality. The objective of this study was to verify whether frequencies between 20-50 Hz are important for walking noise annoyance and to evaluate which impact sound level metric that best correlates with walking noise annoyance. The methodology was to evaluate annoyance based on binaural recordings of walking noise in a two-part listening test. The stimuli were reproduced using a combination of headphones and subwoofer. Two living rooms were evaluated, one lightweight wooden construction and one heavy concrete construction. Both rooms achieved similar weighted impact sound level when evaluated from 50 Hz, but the rated annoyance differed significantly. The need to consider frequencies down to 20 Hz in lightweight constructions was verified. The best correlation between measured impact sound level and subjective response was achieved when the evaluation range was extended down to 20 or 25 Hz using a flat frequency weighting factor.

  • 18.
    Öqvist, Rikard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik. Tyréns AB.
    Measurement and perception of sound insulation from 20 Hz between dwellings2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Population growth and urbanization are projected by the United Nations to add 2,5 billionpeople to the world’s urban population by 2050. We need to construct buildings in anunprecedented scale to meet global housing demand. Sustainable development is critical.Compared to traditional heavy constructions, lightweight wooden constructions are moreenvironmentally friendly and will play a key role in meeting future demands. However, thereare two major problems with lightweight constructions that need to be addressed: 1) Limitedlow frequency sound insulation and 2) Variations in sound insulation.Annoyance from walking sound tend to be higher in lightweight than in heavy constructionseven with the same measured sound insulation. The Swedish research program AkuLiteindicated that the correlation between measured sound insulation and annoyance wassignificantly improved by extending current evaluation methods from 50 Hz down to 20 Hz.Secondly, large variations in sound insulation between nominally identical lightweightconstructions are common, which leads to larger safety margins. By identifying and quantifyingunderlying causes, production costs can be minimized and the performance can be improved.The aim of the thesis is to develop a new evaluation method for impact sound insulation thatbetter correspond to rated annoyance, and to identify and control underlying causes forvariations in sound insulation. The thesis contains six papers.In Paper I and II, sound insulation measurements were carried out in a large number ofnominally identical rooms of two different industrially prefabricated lightweight woodenconstructions. The purpose was to assess and quantify the variations in impact and airbornesound insulation. In Paper I, 30 nominally identical apartments of a volume based system wasevaluated. The apartments on the highest floor achieved significantly better sound insulationdue to the extra weight on lower floors affecting the elastic connections between stories. InPaper II, 18 rooms of a cross-laminated timber system of plate elements were evaluated.Additionally, several potential parameters related to measurement uncertainty wereinvestigated.Paper III deals with measurement uncertainty. An empirical study of reverberation timemeasurements showed that current methods need to be improved, if sound insulationrequirements are to be extended to 20 Hz.Paper IV and V verified that the frequency range 20-50 Hz is important for walking soundannoyance, and that alternative frequency adaptation terms can improve the correlation betweenmeasured impact sound insulation and annoyance ratings. In Paper IV, the methodology was toperform extensive field measurements in apartment buildings of various construction types andto perform questionnaire surveys among the residents. In Paper V, the methodology was toevaluate annoyance based on binaural recordings of walking sound in a two-part listening test.In Paper VI, 70 measurements in a lightweight wooden system were evaluated to quantify thetotal variations in impact and airborne sound insulation from 20 and 50 Hz, respectively. It wasconcluded that the proposed metrics of impact sound insulation were primarily determined bythe impact sound level 20-40 Hz and that the measurement methods must be evaluatedthoroughly to avoid excessive safety margins.

    A new evaluation method for impact sound insulation from 25 Hz, that correspond to the ratedannoyance for both heavy and lightweight constructions is proposed. By using the proposedmethod and attending the specific causes for variations, the lightweight industry will be able todevelop improved multi-story dwellings with higher perceived acoustic quality.

  • 19.
    Johansson, Örjan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Pamidi, Taraka
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Khoshkhoo, Mohammad
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sandström, Åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sustainable and energy efficient leaching of tungsten(W) by ultrasound controlled cavitation2017Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The project aims to use ultrasound controlled cavitation to achieve a more energy efficient leaching process. Locally, collapsing cavitation bubbles cause an extremely high pressure, shock waves and high temperature, which provide an opportunity to perform the leaching process at a much lower temperature than in an autoclave (20 bar overpressure and 220 ° C). The results show that the method works, but that a higher static pressure and thus temperatures are necessary to achieve a leaching recovery rate corresponding to today's autoclave technology. Another process parameter of importance is flow control and the initiation of cavitation bubbles that occur through a geometrically optimized nozzle (orifice plate). Numerical and experimental adaptation of the developed reactor with respect to the leaching conditions (Sodium hydroxide and Scheelite concentrate), required more time than expected. Best test results show that an energy supplement with ultrasonic controlled cavitation of 104 kWh / kg increases the leaching recovery by 21%. The leaching reagent temperature 60° C was determined regarding available reference data and was thought to be close to optimum for intensive cavitation in atmospheric pressure. Optimum temperature relates to the leaching reagent, vaporization temperature, density, boiling point, surface tension, and viscosity. Generally, for leaching is that higher temperatures are required to increase the chemical reaction rate (requires overpressure). The modified reactor principle provides stable results and is possible to scale up. Higher cavitation intensity for shorter finishing time and higher recovery rate require advanced flow induction, multiple excitation frequencies adapted to the optimized reactor geometry, as well as optimal process pressure and temperature.

  • 20.
    Lundkvist, André
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    3D Auditory Displays for Driver Assistance Systems2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    A constantly increasing number of advanced driver assistance systems are implemented in cars.The driver is required to interpret the data reported by these systems while driving, and thereforeit is important to know how the information signals provided by such systems affect the driver.Driving relies to a large extent on vision, and most current advanced driver assistance systemsuse visual information, requiring visual attention from the driver. This conflicts with the drivingtask and leads to an increase in inattention and in cognitive and visual workload. Off-loadingvisually demanding tasks to other sensory modalities should be beneficial in terms of the driver’sability to divide attention resources. The aim of this thesis is to gain knowledge on how the driveris affected by information and interaction with driver assistance systems utilising 3D auditorydisplays. The goal is to provide knowledge of how to create robust interfaces that assist the driverwhile maintaining the necessary safety aspects while driving.The first paper investigated the importance of sound source placement within the car compartment.Since sound can be a very effective means of capturing attention, it could cause dangeroussituations if used in the wrong way. If sound is used to draw attention, one must be sure to notdraw the driver’s attention away from something more critical. The study showed that soundcan improve attention to the road when the sound source location is in front of the driver.Previous research has shown that a combination of sensory modalities increase the robustnessof perception. To avoid additional load on the visual modality, the second paper investigatedthe usefulness of vibrotactile information, in combination with auditory and/or visual signals.There was no significant increase in performance when adding vibration to a sound signal, butvibration and sound on their own led to similar performance. It can be argued, however, thatcombinations are still useful since they reduce the risk of an important signal being missed orneglected. In this investigation, all signals containing a visual component provided the fastestresponse time.The third paper investigated the usefulness of a 3D auditory display applied on a parking assistancesystem. A user study was conducted to evaluate drivers’ workload and performancewhen using different system implementations. It was found that a 3D auditory display was wellreceived as long as the sound only came from one direction at a time. Providing too much informationto the driver by using simultaneous sound sources at different locations was perceived asconfusing and annoying. In some cases, the effort required to perform a successful parking wassignificantly reduced when using a 3D auditory display system compared to a traditional parkingassistance system using only two sound sources. There were also indications that 3D soundcan reduce drivers’ mental workload and frustration with parking assistance systems.Placing sound sources in the car where they are most suitable can be difficult, especially if soundsources outside the car are required. The fourth paper investigated if it would be possible to use acrosstalk cancellation technique in combination with binaural recordings to reproduce 3D audiousing only two loudspeakers in the car compartment. It was found that when the loudspeakersare placed close to the ears of the driver, crosstalk cancellation can be effective inside the car compartment by avoiding strong reflections. Closely placed loudspeakers reduce filter creationcomplexity and improve sound quality.The fifth paper tackles the problems of within-the-head perception and front-back confusion,commonly found in binaural recordings and synthesis. It has been shown that reverberant binauralsounds are perceived more externalised than anechoic sounds, and tend to suffer less fromfront-back confusion. However, information sound signals should rarely be reverberant. Theidea was to create an image-source model with focus on early reflections and compare it withtraditional artificial head recordings. The image-source model performed better than the artificialhead recordings in terms of front-back confusion, and at the same time considerably limitedthe inherent room acoustics in the sound.In conclusion, meaningful and informative sound signals can raise driving performance if theyare placed in front of the driver. This encourages the driver to maintain focus on the road, byusing the attention capture capabilities of sound. A 3D auditory display can be beneficial forsystems such as parking assistance, since it helps lowering driver effort, mental workload andfrustration. Also, 3D auditory displays increase the drivers’ sense of safety and comfort, by augmentingthe drivers’ surrounding and thereby increasing their situational awareness. If a 3Dauditory display should be implemented in the car, a transaural system with crosstalk cancellationshowed promise for virtual sound source reproduction. However, binaural synthesis hasinherent problems that need to be addressed, specifically front-back confusion. It is hard to recommendusing crosstalk cancellation with binaural synthesis at the current state for locationcritical signals due to localisation confusion. However, using more than one modality for informationsignals makes the signals difficult to miss and could also help with the front-back confusionproblem, but further research is needed. If a transaural system with crosstalk cancellationis chosen as reproduction format, make sure to carefully select the loudspeaker placementsin order to avoid as many problems with filter generation as possible, since this will cause errorsin crosstalk suppression and affect the reproduction sound quality. Directive loudspeakersmounted in the neck rest, or ceiling, are good candidates for implementation.

  • 21.
    Ljunggren, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Öqvist, Rikard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Simmons, Christian
    Luleå tekniska universitet.
    An empirical study of the spatial uncertainty of reverberation time measurement below 50 Hz2016Ingår i: InterNoise 2016: 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future / [ed] von Estorff O., Kropp W., Schulte-Fortkamp B, German Acoustical Society , 2016, s. 3661-3665Konferensbidrag (Refereegranskat)
    Abstract [en]

    The relevance of performing reverberation time measurements at very low frequencies became an issue in Sweden when the national standard recommended that impact sound insulation should be evaluated from 20 Hz for sound classes above the minimum requirement. Even though the standard states that L'n,T is not to be normalized with respect of reverberation time for frequencies below 50 Hz, it could be argued to include such a correction term to handle any possible variation in the absorption properties of the room. But this can be done only if the reverberation time can be accomplished with reasonable accuracy. The present paper presents an empirical study where reverberation time has been measured from 20 Hz in two different bedrooms with more than 100 microphone positions in each in order to determine the spatial variation. A comparison is made between the uncertainty as a function of frequency and it is indicated that the standard deviation is larger for the lowest frequencies, below 50 Hz, compared to higher. From an engineering point of view, this can be compensated by adding additional positions to the already existing ISO measurement procedure

  • 22.
    Asplund, Matthias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Rantatalo, Matti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Hiensch, Martin
    Combating curve squeal noise2016Ingår i: Combating curve squeal noise, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Society demand for more sustainable transports is increasing, starting a modal shift from road to railway. The resulting increase in railway traffic intensity is leading to more activities on the track, even during the night time. For many years continuous urbanization has been resulting in a higher density of residents in areas close to railway tracks. The combination of these factors is raising the issue of noise disturbances from railway transports, which is forcing infrastructure managers to take action to combat noise from railway traffic systematically. There are different types of noise emanating from railways and one of the most annoying is curve squeal noise. This paper deals with the curve squeal phenomenon, the places where it occurs, and different methods for reducing it. The curving behaviour of a vehicle plays an important role in the generation of curve squeals, and therefore the way in which different rail profiles affect the capability to steer in a sharp curve is dealt within this paper. The paper is based on two case studies with investigated curves in urban regions that suffer from squeal noise, and in which comparisons between measurements and simulations were performed. The outcome of these studies is a workflow for combating squeal noise, results concerning the effects of a top-of-rail friction modifier on noise mitigation, and a proposed rail profiles for improving the steering capability of vehicles.

  • 23.
    Wijaya, Andi Rahadiyan
    et al.
    Department of Mechanical and Industrial Engineering, Gadjah Mada University, Yogyakarta.
    Johansson, Örjan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Difference thresholds of multi-axis whole-body vibration2016Ingår i: IEEE International Conference on Industrial Engineering and Engineering Management, Piscataway, NJ: IEEE Computer Society, 2016, s. 1760-1764, artikel-id 7798180Konferensbidrag (Refereegranskat)
    Abstract [en]

    A laboratory study was conducted to investigate the effects of lateral and horizontal vibration on the difference threshold of vertical vibration. Twelve male subjects sat on a rigid seat and were exposed to four different vibration conditions (pure vertical vibration; combination of horizontal and vertical vibration; combination of lateral and vertical vibration; combination of horizontal, lateral and vertical vibration). Vertical vibration for four conditions was 5 Hz sinusoidal with a magnitude of 1 ms-2 r.m.s. Horizontal and lateral vibration for the last three conditions were sinusoidal with magnitude 0.5 ms-2 r.m.s. and contained ten frequencies (1 to 8 Hz in third-octave band step). The frequency-weighted acceleration of the ten frequencies was equal. Results showed that horizontal and lateral vibrations have different effects on the difference threshold of vertical vibration. The combination of vertical and horizontal vibration gave a significantly lower difference threshold of vertical vibration than the combination of vertical and lateral vibration

  • 24.
    Johansson, Örjan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Energieffektivisering genom flödesexciterad, resonansförstärkt och ultraljudskontrollerad kavitation: Delprojekt inom Mekmassainitiativet för energieffektivitet (E2MPi)2016Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Projektet syftar till att öka kunskap och förståelse för hur kavitation kan användas och kontrolleras för att koncentrera bearbetningsenergin till frekvensområden som ger effektiv påverkan av cellulosafibrer. Tanken är att skapa ett komplement eller en alternativ teknik till dagens raffinörer. Idén bygger på att resonansförstärkt ultraljud initierar och kollapsar kavitationsbubblor på ytan av cellulosafibrer i vatten. Tidigare forskning har visat att ultraljudsbehandling ger önskade effekter på fiberväggen. Energieffektiviteten har dock inte varit tillräckligt bra och uppskalning är en identifierad problematik. Den föreslagna metoden syftar till att via numerisk och experimentell optimering åstadkomma en energieffektiv och kontrollerad bearbetning av fiberväggen. Den långsiktiga målsättningen är att halvera energiförbrukningen i jämförelse med dagens raffinörer.Hypotesen är att ultraljudskontrollerad kavitation fungerar beroende på att transient asymmetrisk kollapsa av kavitationsbubblor kan ge upphov till extrema tryck på en liten yta. Principen bygger på små att gasbubblor i vatten exciteras av högintensivt ultraljud. Vid en viss kritisk storlek kommer bubblan i resonans och då växer den snabbt. Yttre trycket når sitt max i samband med att bubblan kollapsar. Ultraljud med konstant frekvens (ex 20 kHz) gör att mängder av bubblor, med varierande storlek och harmoniskt relaterade resonansfrekvenser, kollapsar. De jetstrålar i mikroskala som uppstår vid asymmetrisk kollaps av kavitationsbubblor antas ge en mekanisk påverkan av cellulosafibrer i form av både inre och yttre fibrillering.Projektet har resulterat i en utveckling och verifiering av en FE-baserad optimeringsstrategi för flödesinducerad och ultraljudskontrollerad kavitation. Den framtagna kavitationsreaktorn består av en dysa och ett vattenfyllt reaktorrör exciterat med ultraljud. Fibersuspensionen strömmar genom ett inre tunnväggigt rör i reaktorns centrum. Beräkningsmodellen ger stabila resultat avseende ultraljudsexcitering och är kalibrerad med experimentellt bestämda förlustfaktorer för aktuell prototypreaktor. Simuleringar av flödesinducerad kavitation begränsades till ren vattenfas. Den framtagna geometrin är dock verifierad avseende strömning med fibersuspension. Experimentella resultat utan flöde visar mycket god överenstämmelse avseende beräknade svängningsformer och resonansfrekvenser. Beräknad ljudtrycksnivå är högre än uppmätt beroende på de olinjäriteter som uppstår när vätskan utsätts för mycket höga amplituder. Dessutom är förlustfaktorn något högre i experimenten och trycksignalens verkliga effektinnehåll ligger delvis utanför mätområdet.Beräkningsjämförelser med ett alternativt och kommersiellt förekommande reaktorkoncept (behållare), visar att den nyutvecklade rörreaktorn ger högre intensitet i den optimala zonen (+120%). Den totala förlustfaktorn för rörreaktorn är ca 1.1 % vid resonans. Tillförd elektrisk effekt bestäms genom att mäta ström och spänning när kavitationsreaktorn exciteras vid sin resonansfrekvens. Optimal kavitationseffekt identifieras av ljudtrycksamplitudkvoten: pUS(f1.5)/pUS(f1). Kavitation ger effektiv bearbetning av fibermaterialet i zonen för maximal tryckvariation. Initiering av flödesinducerad kavitation med justerbar Venturi-dysa ger intensivare kavitation samt god blandning och sammanhållen fibersuspension. Test och verifiering med fibermaterial är baserad på en HT-CTMP fiber (torkad/aldrig torkad) med 0.5%, 1% och 2% konc. Positiv förändring av fiberkvalitet uppstod endast i några av testfallen. I test med både flödesinducerad och ultraljudsstyrd kavitation uppstod bäst resultat vid lägst energinivå (470 kWh/adt). I övriga testfall finns misstanke om att fibermaterialet har förstörts av för hög kavitationsintensitet. En slutsats som delvis verifieras av SEM-analys av behandlat fibermaterial. Tillförd energinivå var dock inte tillräcklig för att uppnå godkänd massakvalitet, dvs. lika bra eller bättre dragindex. I nuläget går det inte att fastställa om föreslagen metod är energieffektiv på grund av svårigheten i att jämföra en prototyp och fullskaleanläggning. En uppenbar förbättringsmöjlighet med framtagen reaktorlösningen är att förlänga reaktorröret (ej realiserbart i prototypskedet). Den valda reaktorlösningen kan skalas upp genom parallellkoppling och seriekoppling. Seriekoppling och längre reaktorrör kräver ett högre matningstryck vilket kan ge en fördel med högre kavitationsintensitet. Den experimentella valideringen är begränsad till en excitationsfrekvens (22.7 kHz) och normaltryck. En kombination med högre ultraljudsfrekvenser (37 och/eller 53 kHz för rörreaktorn) är en möjlig förbättring genom att de aktiva bubblornas storlek reduceras och får en storleksordning som är bättre anpassad till fiberväggens storlek och struktur. En annan förbättringsaspekt är ett högre statiskt tryck, vilket ökar kavitationsintensiteten och möjliggör en förkortad exponeringstid.

  • 25.
    Ågren, Anders
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Ljunggren, Fredrik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    In situ measured flanking transmission in light weight timber houses with elastic flanking isolators: Part II2016Ingår i: InterNoise 2016: 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future / [ed] von Estorff O., Kropp W., Schulte-Fortkamp B, German Acoustical Society , 2016, s. 3772-3781Konferensbidrag (Refereegranskat)
    Abstract [en]

    There is a strong trend to industrially produce multi-storey light weight timber based houses. The concept allows the buildings to be manufactured to a more or less prefabricated extent. Most common types are volume/room modules or flat wall and floor modules. When assembling the modules at the building site, elastomer isolators are used in several constructions to reduce flanking transmission. The sound insulation demands in the Nordic countries are relatively high and therefore the flanking transmission must be well controlled, where elastomer isolators are an established alternative. Decoupled shielding wall elements is another. There are though no working studies or mathematical models of the performance of these isolators. They are treated as simple mass-springs systems that operate vertically, i.e. one degree of freedom. In this paper there are analyses of an expanded set of experimental data of the structure borne sound isolating performance of elastomer isolators, which are separating an excited floor from receiving walls. This part II study now includes all in all 9 buildings. The isolation performance dependence on structure type is analyzed. An empirically based regression model of the vibration level difference is derived. The model is based on measurements of 8 elastomer field installations, which are compared to an installation without elastomers. A goal is that the data can be used for input in future SEN prediction models for modeling of the flanking transmission part of sound insulation

  • 26.
    Andersson, Andreas
    et al.
    Electric Propulsion Systems Department, Volvo Car Group, Gothenburg, Sweden.
    Lennström, David
    oise, Vibrations, and Harshness Department, Volvo Car Group, SE-405 31 Gothenburg.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Influence of Inverter Modulation Strategy on Electric Drive Efficiency and Perceived Sound Quality2016Ingår i: IEEE Transactions on Transportation Electrification, ISSN 2332-7782, Vol. 2, nr 1, s. 24-35Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents an evaluation of differentmodulation techniques and different levels of switching frequencyrandomization for a rear axle electrical drive unit used in auto-motive applications. Inverter and machine losses, and perceivedsound quality of high-frequency acoustic noise are investigated byfinite element calculations, experimental testing, and subjectivenoise assessment. Additionally, stator current harmonics, airgapflux density harmonics, and force density harmonics are comparedfor space vector modulation (SVM) and discontinuous pulsewidthmodulation through finite element modeling. The main conclusionis that, primarily in the field weakening region, significant energysavings can be achieved (up to 17% decrease in total inverter losseswith a switching frequency of 10 kHz). This is obtained withoutdeterioration of perceived sound quality by the use of discontinu-ous pulsewidth modulation with switching frequency randomiza-tion. Furthermore, randomization of the switching frequency doesnot improve the perceived sound quality of the acoustic noise whenusing SVM. However, for discontinuous pulsewidth modulation,improvements in perceived sound quality when randomizing theswitching frequency are observed, primarily below base speed.

  • 27.
    Ekeroot, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Medier ljudteknik och upplevelseproduktion och teater.
    Berg, Jan
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Medier ljudteknik och upplevelseproduktion och teater.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Ranking criticality of stimuli for listening tests2016Manuskript (preprint) (Övrigt vetenskapligt)
  • 28.
    Lundkvist, André
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Response Times for Visual, Auditory and Vibrotactile Directional Cues in Driver Assistance Systems2016Ingår i: SAE International Journal of Transportation Safety, ISSN 2327-5626, E-ISSN 2327-5634, Vol. 4, nr 1, s. 8-14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The number of advanced driver assistance systems is constantly increasing. Many of the systems require visual attention, and a way to reduce risks associated with inattention could be to use multisensory signals. A driver's main attention is in front of the car, but inattention to surrounding areas beside and behind the car can be a risk. Therefore, there is a need for driver assistance systems capable of directing attention to the sides. In a simulator study, combined visual, auditory and vibrotactile signals for directional attention capture were designed for use in driver assistance systems, such as blind spot information, parking assistance, collision warnings, navigation, lane departure warning etc. An experiment was conducted in order to measure the effects of the use of different sensory modalities on directional attention (left/right) in driver assistance systems. Attention was assessed in a driving simulator using Lane Change Task together with a secondary task, designed to measure choice response times and error rates to directional (left/right) information for multisensory signals. Different combinations of visual, auditory and vibrotactile signals were tested and compared. Visual signals alone (when captured by the driver) or in combination with other modalities provided shortest response times (570 ms on average). Auditory and vibrotactile signals captured attention equally well in terms of response time (650 ms and 740 ms on average). No significant differences in localization error rates were observed.

  • 29.
    Nykänen, Arne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Lopez, Mariana
    Anglia Ruskin University.
    Toulson, Rob
    Anglia Ruskin University.
    Safe and Sound Drive: Design of Interactive Sounds Supporting Energy Efficient Behaviour2016Ingår i: Proceedings of the Interactive Audio Systems Symposium, September 23rd 2016, York: Audio Lab, The Department of Electronics, The University of York, 2016Konferensbidrag (Refereegranskat)
  • 30.
    Nykänen, Arne
    et al.
    Cultures of Digital Economy Research Institute, Anglia Ruskin University, Cambridge.
    Lundkvist, André
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Lindberg, Stefan
    Interactive Institute, Piteå.
    Lopez, Mariana
    Cultures of Digital Economy Research Institute, Anglia Ruskin University, Cambridge.
    Safe and Sound Drive: Sound Based Gamification of User Interfaces in Cars2016Ingår i: Proceedings of the AES International Conference / [ed] Spriet A.,Murphy D.,Goetze S, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Safe and Sound Drive project concerns the design of an audio-only serious game for cars that will help drivers to increase eco-driving skills, lower fuel consumption and encourage safe and environmentally friendly approaches to driving. Methods and procedures for the design of sounds for audio-only user interfaces are reviewed and discussed, and design work and preliminary results from user studies of prototypes of the audio interface are presented. Contextual Inquiry Interviews with three participants using the audio interface in a car while driving on a test track showed that opinions about beeps and audio signals vary among subjects. Music and podcast based contents were generally well received. Alteration of media content, e.g. by actively adjusting BPM, volume, spectral balance, or music mix could form working mechanisms for providing game related cues to the driver.

  • 31.
    Lundkvist, André
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Signal Sound Positioning Alters Driving Performance2016Ingår i: SAE International Journal of Transportation Safety, ISSN 2327-5626, E-ISSN 2327-5634, Vol. 4, nr 1, s. 1-7, artikel-id 2015-01-9152Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many of the information systems in cars require visual attention, and a way to reduce both visual and cognitive workload could be to use sound. An experiment was designed in order to determine how driving and secondary task performance is affected by the use of information sound signals and their spatial positions. The experiment was performed in a driving simulator utilizing Lane Change Task as a driving scenario in combination with the Surrogate Reference Task as a secondary task. Two different signal sounds with different spatial positions informed the driver when a lane change should be made and when a new secondary task was presented. Driving performance was significantly improved when both signal sounds were presented in front of the driver. No significant effects on secondary task performance were found. It is recommended that signal sounds are placed in front of the driver, when possible, if the goal is to draw attention forward.

  • 32.
    Mishra, Madhav
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Odelius, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Rantatalo, Matti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Larsson, Jan-Olof
    SKF Sweden.
    Bellander, Magnus
    SKF Sweden.
    Niemi, Ingemar
    Billerud Karlsborg AB.
    Simulations and measurements of the dynamic response of a paper machine roller2016Ingår i: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 58, nr 4, s. 210-212Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The paper industry is a highly automated industry that includes many different production steps, in which a variety of machine components are used. In a paper machine, where the pulp is being transformed into paper, rotating components such as bearing-mounted rollers play an important part in driving the wire with the pulp through the process. In this type of industry with a serial layout, the failure of a single roller or bearing could lead to the stoppage of several production steps, with costly consequences as a result. To ensure and optimise asset availability, a condition-based maintenance (CBM) strategy could be implemented. However, CBM is dependent on an appropriate condition monitoring (CM) technique to detect a physical phenomenon that defines the state of critical components or systems. For the development of CM techniques, it is therefore important to understand and model the physical behaviour of the system in question. In this paper, the behaviour of a roller in a paper machine is analysed using the finite element method (FEM). The physical model was compared with vibration measurements collected from an online monitoring system and an experimental modal analysis.

  • 33.
    Ljunggren, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Öqvist, Rikard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Simmons, Christian
    Luleå tekniska universitet. Simmons akustik och utveckling, Gothenburg, Sweden.
    Uncertainty of in situ low frequency reverberation time measurements from 20 Hz: An empirical study2016Ingår i: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 64, nr 6, s. 706-715Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Measuring reverberation time is normally one of the steps within the procedure of determining sound insulation in dwellings where 100 or 50 Hz usually serves as the lower frequency limit. However, even lower frequencies have become a matter of interest as research in the field recently indicated that the range 20-50 Hz seems to be of great importance when it comes to the perception of impact sound in lightweight buildings. A major issue in this context is then whether it is appropriate to measure and evaluate reverberation time at such low frequencies. This paper presents an empirical study of reverberation time measurements made in two rooms using more than 100 microphone positions in each. The measurement uncertainty with respect to microphone position and combinations of positions are compared for the frequency bands from 16 to 1600 Hz. Furthermore, it is analyzed how many microphone positions are needed in order to, with a reasonable probability, end up with an uncertainty in the related standardized impact sound level insulation L′n,T within ±1 dB

  • 34.
    Lennström, David
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Olsson, Magnus
    Volvo Car Corporation, Dept. 91600/PV2C2.
    Wullens, Frédéric
    Volvo Car Corporation, Dept. 91600/PV2C2.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Validation of the blocked force method for various boundary conditions for automotive source characterization2016Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 102, s. 108-119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vibro-acoustic source characterization is an essential task in vehicle development to enable prediction of receiver response. For structure-borne noise, the interface forces in multiple degrees of freedom due to internal loads are often quantified for root cause analyses in a single system assembly, as in transfer path analysis (TPA). However, for a reliable prognosis of the acoustic performance of a known component such as a motor or pump, a receiver-independent source characterization is required, and the method of acquiring blocked forces from in-situ measurements has been shown to be a preferred technique for such purposes. The benefits of the method are the characterization of the intrinsic properties of the source and the possibilities of measuring the component attached to receivers with varying dynamic properties.There is to date a limited number of validation cases where blocked forces from in-situ measurements are acquired for automotive source–receiver assemblies. In this study the blocked forces of a vacuum pump in nine degrees of freedom were determined when connected to a bracket whose boundary conditions were modified in order to achieve four assemblies with different source/receiver dynamic properties. The results show that the blocked forces are transferable, i.e. the receiver response in one assembly was predicted in a wide frequency range by combining source–receiver transfer functions of that assembly with blocked forces estimated in another assembly. Furthermore, an in-situ blocked force TPA was applied to a double-isolated complete vehicle source–receiver case of an electric rear axle drive with interior compartment sound pressure as target. The reconstructed magnetic tonal harmonics agreed with the measured target response in the frequency range 50–500 Hz, which further motivates the use of the blocked force principles for TPA and source requirements specifications.

  • 35.
    Löfdahl, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    An auralization model for structure-borne tire noise2015Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 96, s. 61-67Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the automotive industry, a Noise, Vibration, and Harshness (NVH) issue such as road noise is an important factor for the perceived quality of a product. A useful method to address NVH problems and to reduce field-testing is to combine recordings and simulations into auralizations. The objective of this paper was to develop an auralization model of structure-borne tire noise based on operationally measured hub forces and validate it by comparison with artificial head recordings made under the same conditions. To create auralizations under the same condition as the recordings, the wheel hub forces used for the recordings were measured and filtered through experimentally measured binaural transfer functions from the same hub of the car to an artificial head in the cabin of the car. The auralization model was validated in a listening test where the criterion for considering the auralizations to be sufficiently similar to the recordings was that eight different tires should be ranked equally in a listening test regardless of whether the test was based on auralizations or recordings. Listening test results from ranking of tires with respect to the annoyance of interior sounds showed good agreement between auralizations and recordings. There were no significant differences between rankings based on recordings and auralizations – except for tires assessed to be very similar – at either 50 km/h or 70 km/h. The conclusion was that the use of auralizations for ranking of structure-borne tire noise gives results that match listening tests based on recordings, and this supports the validity of the auralization model.

  • 36.
    Lennström, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Assessment and control of tonal components in electric vehicles2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    New challenges arise for noise, vibration and harshness (NVH) engineers when electric motors are introduced into cars traditionally powered by internal combustion engines (ICE). The noise signature from an electric traction motor is characterized by speed-dependent high frequency tonal components due to electro-magnetic excitation. Despite the relatively low overall levels, those tonal components can be prominent and contribute to perceived annoyance for the occupants inside the car. With the rapid increase of various types of hybrid/electric vehicles (EV), new methods are required to secure a desired sound quality in future electric vehicle launches. The objective of this thesis was to explore the audible perception of the electric powertrain and develop and validate experimental methods for assessment of noise transmission. The thesis is based upon seven papers. Four of the papers are oriented around tools and techniques for sound quality assessments of EV-noise. Due to the specific character, there is a proven need for engineers to identify relevant psycho-acoustic metrics for quantifying the subjective perceptions of an accelerating EV. The relationship between the metric prominence ratio (PR) and perceived annoyance was explored and requirement criteria were proposed. PR is appropriate for quantifying individual tonal components, well frequency separated from each other. For more complex sounds, e.g. with multiple proximate prominent tones, the suitability of this metric is questioned. Therefore, the harmonic content of a large number of EVs on the market was examined in order to bring further facts to the on-going discussion on sound quality quantification of EV specific noise. Furthermore, the assessment environment’s role as well as the impact of experiencing the sound sensation in the real environment for sound quality evaluations were studied. Finally, perception of the tonal components related to different DC/AC conversion techniques including randomized pulse-width modulation was explored.The main mechanical system properties that are responsible for the airborne radiation and transfer of electric powertrain induced noise were studied. The acoustic transfer functions’ (ATF) spatial resolution with respect to estimated interior noise was investigated for theoretically derived and measured surface vibrations. ATFs and surface velocities are also central for the presented in-situ method for determination of radiated sound power from the stator housing due to a dominant order. By acquiring the operational deflection shape due to an electro-magnetic radial force wave, a simplified expression for estimation of the radiation efficiency was derived. The two papers highlight the advantages of the rotational symmetric force excitation acting on the stator housing which enables sound power to be used as an acoustic source characterization, which perhaps is the most adequate measure for system target setting directed towards external suppliers. The final contribution of methods for handling EV-specific noise concerns structure-borne sound. The method of in-situ estimation of blocked forces, a theoretically independent source characterization, is evaluated for transfer path analysis (TPA) of a double isolated electric rear axle drive. The method has two main advantages; it is substantially faster compared to the conventional TPA method and the blocked forces allow for accurate prediction of the acoustic response when the same source is being integrated with a different receiving structure. The prerequisite for the second is that the source activity remains invariant and this was further studied.In summary, the work reported in this thesis is intended to support engineers to succeed with the acoustic refinement and thereby also to contribute to increasing competitiveness of hybrid/electric vehicles. Keywords: Electric motor acoustic noise, sound quality, sound power, NVH, vehicle acoustics, blocked force

  • 37.
    Nykänen, Arne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Lennström, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Car Ride Before Entering the Lab Increases Precision in Listening Tests2015Ingår i: SAE International Journal of Passenger Cars - Mechanical Systems, ISSN 1946-3995, E-ISSN 1946-4002, Vol. 8, nr 3, s. 982-988Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Subjects who are well aware of what to judge commonly yield more consistent results in laboratory listening tests. This awareness may be raised by explicit instructions and training. However, too explicit instructions or use of only trained subjects may direct experiment results in an undesired way. An alternative is to give fairly open instructions to untrained subjects, but give the subjects a chance to get familiar with the product and context by, for example, riding a representative car under representative driving conditions before entering the laboratory. In this study, sound quality assessments of interior sounds of cars made by two groups were compared. In one group subjects were exposed to the same driving conditions that were later assessed in a laboratory listening test by taking them on a ride in one of the cars to be assessed, just before entering the laboratory. In the other group subjects made the laboratory assessments without prior car riding. In the laboratory, sound quality was assessed for binaurally recorded interior sounds of cars reproduced through headphones. The results showed that even though average sound quality assessments in most cases were the same for both groups, the variances were significantly smaller for the group where subjects had been taken on the car ride before the listening test. A conclusion is that being exposed to the sounds in the right context just before the listening test, e.g. by riding a representative car under representative driving conditions, can increase the precision in laboratory sound quality assessments.

  • 38.
    Lennström, David
    et al.
    Volvo Car Corporation.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Interior sound of today's electric cars: Tonal content, levels and frequency distribution2015Ingår i: SAE technical paper series, ISSN 0148-7191, Vol. 2015-01-2367Artikel i tidskrift (Refereegranskat)
  • 39.
    Löfdahl, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Prominence of Different Directions of Hub Forces and Moments in Structure-Borne Tire Noise2015Ingår i: SAE International Journal of Passenger Cars - Mechanical Systems, ISSN 1946-3995, E-ISSN 1946-4002, Vol. 8, nr 1, s. 346-353, artikel-id 2015-01-9106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the automotive industry, tire noise is an important factor for the perceived quality of a product. A useful method to address such NVH problems is to combine recordings with measurements and/or simulations into auralizations. An example of a method to create structure-borne tire noise auralizations is to filter recordings of hub forces and moments through binaural transfer functions experimentally measured from the hub of the car to an artificial head in the car cabin. To create authentic auralizations of structure-borne sound, all six degrees of freedom (DOFs) of hub forces and moments and transfer functions should be included. However, rotational DOFs are often omitted due to measurement difficulty, complexity, time, and cost. The objective was to find which DOF (or DOFs) is perceived as most prominent in structure-borne tire noise. An auralization model of interior structure-borne tire noise was used. An auralization including all DOFs was compared with auralizations lacking one DOF at a time in a listening test. Auralizations lacking either all translational DOFs or all rotational DOFs were also included. Results from the listening test showed that the overturning moment (Mα) was perceived as the most prominent DOF. Removing all rotational DOFs led to a larger audible difference than removing all translational DOFs. Therefore, rotational DOFs should not be disregarded in tire noise auralization. The results suggest which DOFs are important to consider in tire and vehicle sound design.

  • 40.
    Mishra, Madhav
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Odelius, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Rantatalo, Matti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Larsson, Jan-Olof
    SKF Sweden.
    Bellander, Magnus
    SKF Sweden.
    Niemi, Ingemar
    Billerud Karlsborg AB.
    Simulations and Measurements of the Dynamic Response of a Paper Machine Roller2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    The paper industry is a highly automated industry that includes many different production steps where a variety of machine components are used. In the paper machine where the pulp is being transformed into paper, rotating components like bearing mounted rollers play an important part to drive the wire with the pulp through the process. In this type of industry with a serial layout, the failure of a single roller or bearing could lead to stoppage of several production steps with costly consequences as a result. To ensure and optimize the asset availability, a condition based maintenance (CBM) strategy could be implemented. However, CBM is dependent on an appropriate condition monitoring (CM) technique to detect physical phenomenon that defines the state of critical components or systems. For the development of CM techniques, it is therefore important to understand and model the physical behaviour of the system in question. In this paper the behaviour of a roller in a paper machine is analysed using finite element method (FEM). The physical model was compared with vibration measurements collected from an online monitoring system and an experimental modal analysis.

  • 41.
    Nykänen, Arne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Wingstedt, Johnny
    Dalarna University, Sound and Music Production, Dalarna University.
    Sundhage, Johan
    Klevgränd Produktion, Klevgränd 1B, 116 46 Stockholm.
    Mohlin, Peter
    Semcon AB.
    Sketching Sounds: listening, moving and listening again2015Ingår i: Design Studies, ISSN 0142-694X, E-ISSN 1872-6909, Vol. 39, s. 19-47Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, the use of sketching in sound design was studied. Based on Schon and Wiggins' model of how designers use sketching to see, move, and see again, we suggest that sound design evolves through a similar process requiring listening, moving, and listening again. This is facilitated by considering sounds as sketches. A case was followed in which six designers were asked to design a sound logotype. Processes and interactions were studied. The results suggest that sound design can be considered as a listen – move – listen process. Sound design is a conversation with sounding material, crucially dependent on listening. To assist in this, a computer interface was developed. Analysis of its use suggests that it supported co-designing.

  • 42.
    Johnsson, Roger
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Odelius, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Rantatalo, Matti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    A new test track for automotive squeak and rattle (S&R) detection2014Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 80, s. 79-85Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The perceived quality of interior sounds is of increasing importance in the automotive industry since it is important for the customer perception of vehicle quality. Squeak and rattle (S&R) is a group of intermittent interior noise that reduce the sense of quality dramatically. To identify and solve S&R problems the car manufacturers do both simulations and tests in laboratory of complete vehicles as well as subsystems. As a complement, to laboratory testing and for verification, complete vehicle tests at proving grounds are done. In order to systematically test for vehicle S&R noise at proving grounds there is a need for a new type of test track that in a controlled and repetitive ways excite vehicles at different frequencies. This paper describes such a new test track, called the Frequency Sweep Test Track (FSTT). The test track is based on sweep excitation and improves the precision when detecting and solving S&R issues. Different design considerations such as sweep waveform, frequency range and sweep rate are discussed. The track design is evaluated using a quarter-car model including a tandem ellipsoid tyre model. In a case study a FSTT was built and the excitation of a car was measured. The track excited the expected frequency range and the track operated well in detecting a rattle in the dashboard of an executive production car and at which frequency the rattle occurred.

  • 43.
    Löfdahl, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Auralization of structure-borne tire noise2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 44.
    Ljunggren, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Simmons, Christian
    Luleå tekniska universitet.
    Högberg, Klas
    WSP Acoustics, Ullevigatan 19, 41140 Gothenburg.
    Correlation between sound insulation and occupants’ perception: Proposal of alternative single number rating of impact sound2014Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 85, s. 57-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Traditionally, multi-family houses have been constructed using heavy, homogenous materials like concrete and masonry. But as a consequence of the progress of lightweight building systems during the last decades, it has been questioned whether standardized sound insulation evaluation methods still are appropriate.An extensive measurement template has been applied in a field survey where several vibrational and acoustical parameters were determined in ten Swedish buildings of various constructions. In the same buildings, the occupants were asked to rate the perceived annoyance from a variety of natural sound sources. The highest annoyance score concerned impact sounds, mainly in the buildings with lightweight floors.Statistical analyses between the measured parameters and the subjective ratings revealed a useful correlation between the rated airborne sound insulation and Rw′+C50–3150 while the correlation between the rated impact sound insulation and Ln,w′+CI,50–2500 was weak. The latter correlation was considerably improved when the spectrum adaptation term with an extended frequency range starting from 20 Hz was applied. This suggests that frequencies below 50 Hz should be considered when evaluating impact sound in lightweight buildings.

  • 45.
    Ekeroot, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Medier ljudteknik och upplevelseproduktion och teater.
    Berg, Jan
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Medier ljudteknik och upplevelseproduktion och teater.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Criticality of audio stimuli for listening tests: listening durations during a ranking task2014Ingår i: 136th Audio Engineering Society Convention 2014, Red Hook, NY: Curran Associates, Inc., 2014, s. 114-122Konferensbidrag (Refereegranskat)
    Abstract [en]

    The process of selecting critical audio stimuli for listening tests is known from the literature to be both labor-intensive and time-consuming, and has been described as more of art than science. Explicit accounts of systematic procedures are not the most commonly encountered. In a previous study a ranking-by-elimination method was investigated, resulting in a rank order that could be used as a guide for critical stimuli selection. This paper presents a further exploratory analysis of data on the subjects’ listening durations, both as a function of number of stimuli left on screen and individually per stimulus. A strong negative correlation was found between the rank order of criticality and playing duration.

  • 46.
    Poll, Marijke Keus van de
    et al.
    Department of Building, Energy, and Environmental Engineering, University of Gävle.
    Ljung, Robert
    Department of Building, Energy, and Environmental Engineering, University of Gävle.
    Odelius, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Sörqvist, Patrik
    Department of Building, Energy, and Environmental Engineering, University of Gävle.
    Disruption of writing by background speech: The role of speech transmission index2014Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 81, s. 15-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Speech transmission index (STI) is an objective measure of the acoustic properties of office environments and is used to specify norms for acceptable acoustic work conditions. Yet, the tasks used to evaluate the effects of varying STIs on work performance have often been focusing on memory (as memory of visually presented words) and reading tasks and may not give a complete view of the severity even of low STI values (i.e., when speech intelligibility is low). Against this background, we used a more typical office-work task in the present study. The participants were asked to write short essays (5 min per essay) in 5 different STI conditions (0.08; 0.23; 0.34; 0.50; and 0.71). Writing fluency dropped drastically and the number of pauses longer than 5 s increased at STI values above 0.23. This study shows that realistic work-related performance drops even at low STI values and has implications for how to evaluate acoustic conditions in school and office environments

  • 47.
    Ljunggren, Fredrik
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Is it necessary to measure impact sound insulation from 20 Hz in lightweight multi-storey buildings?2014Konferensbidrag (Refereegranskat)
  • 48.
    Nykänen, Arne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Lindegren, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Wruck, Louisa
    Ljung, Robert
    University of Gävle.
    Odelius, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Möller, Sebastian
    TU Berlin.
    Memory of AMR coded speech distorted by packet loss2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Previous studies have shown that free recall of spoken word lists is impaired if the speech is presented in background noise, even if the signal-to-noise ratio is kept at a level allowing full word identification. The objective of this study was to examine recall rates for word lists presented in noise and word lists coded by an AMR (Adaptive Multi Rate) telephone codec distorted by packet loss. Twenty subjects performed a word recall test. Word lists consisting of ten words were played to the subjects. The subjects repeated each word immediately after it had been played, to ensure that the words were heard correctly. After the complete list had been played the subjects wrote down all words remembered. In this way, both word identification and recall rates were measured. Three distorted conditions were compared with an undistorted control condition using a within-subject design: speech spectrum weighted noise at 4 dB SNR, and AMR coded speech with two levels of packet loss, one mild and one severe. The results confirmed the disruptive effect of noise on free recall of words, while no significant impairment was found for the AMR distortions. The noise and the AMR coding with mild packet loss gave approximately the same impairment of word identification. The AMR coding with severe packet loss gave a larger impairment of word identification, even though the word recall rate was unaffected. This result suggests that packet loss in AMR coded speech causes distortions which disrupt recall of words less than noise at levels resulting in the same change of word identification rates. Since impairment of word identification rates did not correlate with impairment of word recall rates models for quality prediction of speech reproductions should not be based on identification rates alone.

  • 49.
    Löfdahl, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nykänen, Arne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Mobility measurement in six DOFs applied to the hub of a car2014Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 83, s. 108-115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Complex models are usually needed to predict functional performance of mechanical devices such as noise and vibration levels. A typical model is divided into substructures where each substructure is described either as a simulation or as an experimental model. When coupling substructures, information is needed that describes the boundary conditions at the attachment points of the various substructures. This can be hard to achieve, especially when full structural behavior including rotational degrees of freedom (DOFs) are needed. The objective of this study was to obtain the mechanical mobility matrix in six DOFs for a wheel hub of car, as an example of a complex mechanical structure, through an experimental approach based on the multiple-input multiple-output technique. Further, evaluation of the measurement quality was conducted without requirements for numerical simulation comparisons. A specially designed brake disc was fabricated for direct attachment of shakers and transducers. The quality of the 6-DOF mechanical mobility matrix was evaluated using reciprocities, coherence functions, and random error in the gain-factor estimates. The results showed good quality in the reciprocities, and the multiple coherences in each degree of freedom were close to one in the frequency range of 25–500 Hz. The random error can be reduced by increasing the number of averages.

  • 50.
    Shah, Ashish
    et al.
    Volvo Car Group.
    Lennström, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik. Volvo Car Group.
    Sturesson, Per-Olof
    Volvo Car Group.
    Easterling, William
    Volvo Car Group.
    NVH Integration of Twin Charger Direct Injected Gasoline Engine2014Ingår i: SAE International Journal of Passenger Cars - Mechanical Systems, ISSN 1946-3995, E-ISSN 1946-4002, Vol. 7, nr 3, s. 1221-1228Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increased focus and demands on the reduction of fuel consumption and CO2 requires the automotive industry todevelop and introduce new and more energy efficient powertrain concepts. The extensive utilisation of downsizingconcepts, such as boosting, leads to significant challenges in noise, vibration and harshness (NVH) integration. This is inconflict with the market expectation on the vehicle's acoustic refinement, which plays an increasingly important role interms of product perception, especially in the premium or luxury segment. The introduction of the twin charger boostingsystem, i.e. combining super and turbo charging devices, enables downsizing/speeding in order to achieve improved fueleconomy as well as short time-to-torque, while maintaining high driving dynamics. This concept requires also extensiveconsideration to NVH integration. The NVH challenges when integrating a roots type supercharger are very extensive. Thehigh frequency source characteristics of the supercharger result in complex wave propagation inside the intake ductsystem since exciting pulsation orders are well above duct cut-on frequencies. The source strength in relation to audibleinterior tonal noise threshold is also very high. In addition the background masking levels in terms of mainly combustionrelated powertrain and road noise are low with the consequence that the orders (tonal noise components) can beprominent and annoying even with a high degree of acoustic source treatment (remedies). The scope of this paper is todescribe quantification of the charging system noise radiation and propagation including subsystem target cascadingsynthesis.

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