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  • 1.
    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.
    Shankar, Vijay
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Comparison of two different ultrasound reactors for the treatment of cellulose fibers2020Ingår i: Ultrasonics sonochemistry, ISSN 1350-4177, E-ISSN 1873-2828, Vol. 62, artikel-id 104841Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The pulp and paper industry is in continuous need for energy-efficient production processes. In the refining process of mechanical pulp, fibrillation is one of the essential unit operations that count for up to 80% of the total energy use. This initial study explores the potential and development of new type of scalable ultrasound reactor for energy efficient mechanical pulping. The developed reactor is of continuous flow type and based on both hydrodynamic and acoustic cavitation in order to modify the mechanical properties of cellulose fibers. A comparison of the prototype tube reactor is made with a batch reactor type where the ultrasonic horn is inserted in the fluid. The pulp samples were sonicated by high-intensity ultrasound, using tuned sonotrodes enhancing the sound pressure and cavitation intensity by a controlled resonance in the contained fluid. The resonant frequency of the batch reactor is 20.8 kHz and for the tube reactor it is 22.8 kHz. The power conversion efficiency for the beaker setup is 25% and 36% in case of the tube reactor in stationary mode. The objective is to verify the benefit of resonance enhanced cavitation intensity when avoiding the effect of Bjerkenes forces. The setup used enables to keep the fibers in the pressure antinodes of the contained fluid. In case of the continuous flow reactor the effect of hydrodynamic cavitation is also induced. The intensity of the ultrasound in both reactors was found to be high enough to produce cavitation in the fluid suspension to enhance the fiber wall treatment. Results show that the mechanical properties of the fibers were changed by the sonification in all tests. The continuous flow type was approximately 50% more efficient than the beaker. The effect of keeping fibers in the antinode of the resonant mode shape of the irradiation frequency was also significant. The effect on fiber properties for the tested mass fraction was determined by a low-intensity ultrasound pulse-echo based measurement method, and by a standard pulp analyzer.

  • 2.
    Najjarzadeh, Nasim
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Krige, Adolf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Pamidi, Taraka Rama Krishna
    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.
    Enman, Josefine
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Numerical modeling and verification of a sonobioreactor and its application on two model microorganisms2020Ingår i: PLoS ONE, E-ISSN 1932-6203, Vol. 15, nr 3, artikel-id e0229738Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ultrasound has many uses, such as in medical imaging, monitoring of crystallization, characterization of emulsions and suspensions, and disruption of cell membranes in the food industry. It can also affect microbial cells by promoting or slowing their growth and increasing the production of some metabolites. However, the exact mechanism explaining the effect of ultrasound has not been identified yet. Most equipment employed to study the effect of ultrasound on microorganisms has been designed for other applications and then only slightly modified. This results in limited control over ultrasound frequency and input power, or pressure distribution in the reactor. The present study aimed to obtain a well-defined reactor by simulating the pressure distribution of a sonobioreactor. Specifically, we optimized a sonotrode to match the bottle frequency and compared it to measured results to verify the accuracy of the simulation. The measured pressure distribution spectrum presented the same overall trend as the simulated spectrum. However, the peaks were much less intense, likely due to non-linear events such as the collapse of cavitation bubbles. To test the application of the sonobioreactor in biological systems, two biotechnologically interesting microorganisms were assessed: an electroactive bacterium, Geobacter sulfurreducens, and a lignocellulose-degrading fungus, Fusarium oxysporum. Sonication resulted in increased malate production by Gsulfurreducens, but no major effect on growth. In comparison, morphology and growth of Foxysporum were more sensitive to ultrasound intensity. Despite considerable morphological changes at 4 W input power, the growth rate was not adversely affected; however, at 12 W, growth was nearly halted. The above findings indicate that the novel sonobioreactor provides an effective tool for studying the impact of ultrasound on microorganisms.

  • 3.
    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.
    Shankar, Vijay
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Acoustic design principles for energy efficient excitation of a high intensity cavitation zone2019Ingår i: Proceedings of the 23rd International Congress on Acoustics, integrating 4th EAA Euroregio 2019: ICA 2019, 9 - 13 September / [ed] Martin Ochmann, Aachen, Germany, 2019, s. 948-955Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Energy-efficient process intensification is a key aspect for a sustainable industrial production. To improve energy conversion efficiency high intensity cavitation is a promising method, especially in cases where the material to be treated is valuable and on the micro meter scale. Transient collapsing cavitation bubbles gives powerful effects on objects immersed in fluids, like cellulose fibers, mineral particles, enzymes, etc. The cavitation process needs optimization and control, since optimal conditions is multivariate challenge. This study focuses on different design principles to achieve high intensity cavitation in a specific volume in a continuous flow. This study explores some potential design principles to obtain energy efficient process intensification. The objective is to tune several different resonance phenomena to create a powerful excitation of a flowing suspension (two-phase flow and cavitation bubbles). The reactor is excited by sonotrodes, connected to two coupled resonant tube structures, at the critical frequency. Finally cavitation bubbles are initiated by a flow through a venturi nozzle. The acoustically optimised reactor geometry is modelled in Comsol Multiphysics®, and excited by dedicated ultrasound signals at three different frequencies. The effect of the high intensity cavitation is experimentally evaluated by calorimetric method, foil tests and degree of fibrillation on cellulose fibers.

  • 4.
    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 Cavitation Effect in Case of Fixed and Free Fibers in an Ultrasound Beaker2019Ingår i: Proceedings of the 23rd International Congress on Acoustics, integrating 4th EAA Euroregio 2019: ICA 2019, 9 - 13 September / [ed] Martin Ochmann, Aachen, Germany, 2019, s. 8217-8224Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In this study, we investigate the impact of high-intensity ultrasound treatment on the mechanical properties of pulp fibers. The pulp fiber samples are sonicated in an acoustically optimised beaker where high-intensity ultrasound is generated using a tuned sonotrode device. The idea is to create a controlled resonance to efficiently enhance the sound pressure in the beaker. Input power is 90Watt. The objective is to define the difference between freely suspended fibers in a beaker compared to keeping fibers in a fixed position. The hypothesis is that fiber treatment at a specific input power will be more efficient in the case when fibers are kept in a high pressure zone. Since the fiber wall is a layered structure, it is likely to delaminate internally which will affect the mechanical properties of the fiber. The effect on fiber properties is verified by measuring the ultrasound attenuation spectra for the treated fibers. The attenuation measurements are based on measurements of a low-intensity ultrasound pulse-echo technique. On a macroscopic scale, changes in the attenuation spectra relates to a change in mechanical properties of the fiber wall, since the suspended fibers more or less retain their diameter and length distributions.

  • 5.
    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.
    Energy Efficient Fibrillation of Cellulose Fibers using an Ultrasound Reactor2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    The pulp and paper industry is in continuous need for energy-efficient production processes. Therefore, there is a focus in reducing electrical energy use in the production of paper.  The most energy demanding processes are related to fibrillation, which in some cases use up to 80% of required electrical power, with a net efficiency of 1%. The presented work focus on ultrasound controlled cavitation in concentrating the processing energy to provide an energy efficient development of cellulose fibers. The objectives are to develop a scalable cavitation reactor to obtain energy-efficient fibrillation of cellulose fibers aiming at reducing the energy use by 50%. Our goal is to develop a methodology based on multiphysic simulation for the design of an alternative refiner based on ultrasound cavitation. The reactor concept is of a flow through type where cavitation bubbles are initiated in the fiber suspension by the pressure release when the pulp flow through a venturi nozzle. The induced cavitation bubbles are collapsed by high intensity ultrasound at resonant frequencies. The collapsing bubbles and their associated shock waves modify the fiber wall properties which enables fibrillation.  Energy efficient fibrillation of cellulose fibers is therefore possible to achieve through an optimized combination of hydrodynamic and ultrasonic controlled cavitation. Initial results shows a positive effect on fiber quality. However, further optimization of process parameters like temperature and static pressure is required.

  • 6.
    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

  • 7.
    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

  • 8.
    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.

  • 9.
    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

  • 10.
    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.

  • 11.
    Nykänen, Arne
    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.
    Sirkka, Anna
    Interactive Institute – Sonic Studio, Piteå.
    Johansson, Örjan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Assessment of changes in preference ratings of auralized engine sounds caused by changes in frequency resolution of transfer functions2013Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 74, nr 12, s. 1343-1353Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Auralization facilitates aural examination of contributions from different sound sources, individually and as parts of a context. Auralizations can be created by filtering sounds of perceptually salient sources through binaural transfer functions (BTFs) from source positions to a listening position. When such auralizations are used for product sound design it is essential to know that they are of sufficient quality. A basic requirement is that preference ratings are unaffected by the quality of the auralizations. The objective of this study was to measure changes in preference ratings of auralized engine sounds caused by changes in frequency resolution of used BTFs. Auralizations of engine sounds were created by filtering source sounds through BTFs measured from source positions to a driver’s position inside a truck cabin. The BTFs were altered by lowering the frequency resolution and by smoothing in the frequency domain. Preferences for the auralizations were compared using a modified version of the MUlti Stimulus test with Hidden Reference and Anchor, MUSHRA (ITU-R BS.1534-1). Since the use of a reference is only appropriate when a reference known to be most preferred exists the reference was removed, resulting in a MUlti Stimulus Test with Hidden Anchors (MUSTHA). For assessment of the differences between the auralizations a statistical method commonly used for assessing agreement between methods of clinical measurement was adopted. The lowest frequency resolutions resulting in acceptable agreement between preference ratings of auralizations made with high frequency resolution (1 Hz) BTFs and auralizations made with simplified BTFs were 32 Hz frequency resolution or smoothing with either 1/24 octave bandwidth filters or 63 Hz absolute bandwidth filters.

  • 12.
    Wigholm, Pär
    et al.
    ÅF Ljud & Vibrationer.
    Nilsson, Per-Åke
    ÅF Ljud & Vibrationer.
    Johansson, Örjan
    ÅF Ljud & Vibrationer.
    Best avaliable technology: Buller från bergtäkter2013Rapport (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    På uppdrag av Nordiska ministerrådet har ÅFs experter inom ljud och vibrationer utvärderat bästa tillgängliga teknik (BAT-Best Available Technique) avseende buller från bergtäkter. Syftet är att visa hur bullerutbredningen kan variera från en bergtäkt beroende på val av maskinutrustning och tillämpning av bästa möjliga teknik. Riktvärden, villkor och mätmetoder är relativt lika i de Nordiska länderna, men skillnader finns. Analysen fokuserar på de ljudeffekter som olika maskiner och verksamheter ger upphov till, samt vad som normalt görs och kan beaktas i en bergtäkt för att minska bullerspridning till omgivningen. Resultatet visar att med tillämpning av bästa tillgängliga teknik (BAT) kan ljudutbredningen till omgivningen minskas betydligt. Avståndet från täkt till punkt i omgivningen där riktvärdet överskrids kan då halveras jämfört med den bullrigaste situationen. Detta innebär att området som överstiger riktvärdet, med rätt topografiska förutsättningar och tillämpning av BAT, kan minskas ned till en fjärdedel.

  • 13.
    Johansson, Örjan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Schönfeld, Stephan
    ÅF-Infrastructure AB.
    Lindforss, Daniel
    ÅF-Infrastructure AB.
    Sound sketch procedure for auralization of the interior sound of a high speed train2012Ingår i: Proceedings of Inter-Noise 2012: held in conjunction with the annual meeting of the Noise Control and Acoustics Division of the American Society of Mechanical Engineers ; New York, New York, USA, August 19 - 22, 2012 / [ed] Courtney Burroughs, Washington, DC: International institute of noise control engineering , 2012Konferensbidrag (Övrigt vetenskapligt)
  • 14.
    Nykänen, Arne
    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.
    Sirkka, Anna
    Scania, RTRN Acoustics, Truck Development.
    Johansson, Örjan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Assessment of the change in similarity judgements of auralized engine sounds caused by changes in frequency resolution of transfer functions2011Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 72, nr 2-3, s. 115-123Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Auralization facilitates aural examination of contributions from different sound sources, individually and as parts of a context. Auralizations can be created by filtering sounds of the perceptually most salient sources through binaural transfer functions (BTFs) from source positions to a listening position. When psychoacoustic analysis is based on auralizations, the auralizations need to give the same impression as real sounds. The objective of this study was to determine the frequency resolution required for auralizations to be perceptually equivalent to recordings made with an artificial head. Auralizations of the contribution of engine sounds to interior sounds of a truck were examined. In listening tests auralizations based on simplified BTFs were compared to artificial head recordings. The BTFs were simplified by lowering the frequency resolution and by smoothing in the frequency domain. Auralizations made through BTFs with a resolution of 4 Hz or higher or smoothed with maximum 1/96 octave moving average filters were perceived as similar to artificial head recordings.

  • 15.
    Odelius, Johan
    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.
    Self-assessment of classroom assistive listening devices2010Ingår i: International Journal of Audiology, ISSN 1499-2027, E-ISSN 1708-8186, Vol. 49, nr 7, s. 508-517Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Self-assessment of classroom assistive listening devices (ALDs) based on induction loop systems was carried out in Swedish classes for hearing-impaired students. A questionnaire was developed and completed by 25 students (bilateral hearing aid users, 10-20 years old). Responses for hearing aid microphone mode (M) and telecoil mode (T) were collected. Two attributes, audibility and awareness, were identified and assigned to either mode. Better audibility was achieved in T-mode. Students with severe hearing loss benefited more using T-mode when compared to the better hearing students, especially in more difficult listening situations. Better awareness was achieved in M-mode; students could better hear, locate and segregate sounds in the environment around them. Depending on the situation, students make different choices between audibility and awareness. Self-assessment is a promising approach for determining what combination of ALD design and function that will best benefit the students

  • 16.
    Nykänen, Arne
    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.
    Lundberg, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Berg, Jan
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Medier ljudteknik och upplevelseproduktion och teater.
    Modelling perceptual dimensions of saxophone sounds2009Ingår i: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 95, nr 3, s. 539-549Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the past, musical instruments were developed over long periods of time by skilled craftsmen. Today, most instruments are mass-produced. Design of musical instruments as mass-produced products requires using strategies which make it easier to identify customer needs and develop exact specifications. To develop useful specifications it is necessary to convert general descriptions into something which can be commonly understood and also be interpretable in terms of acoustic metrics. In this study, methods for analysis and specification of steady state parts of alto saxophone sounds were developed. Saxophonists' use of verbal descriptions of saxophone sounds was investigated. Sound stimuli were binaurally recorded. Judgements upon perceived qualities were made by saxophonists and non-saxophonists using the method of verbal attribute magnitude estimation. Perceptual dimensions were identified using principal component analysis of listening test data. Three prominent dimensions were found and described using the verbal attributes: 1) warm/soft, 2) back vowel analogues and 3) sharp/rough. The perceptual dimensions were modelled as linear functions of acoustic metrics. The results were validated through listening tests with new subjects and new stimuli. Based on the findings, the method was seen as an approach which can enhance the musical instrument design process.

  • 17.
    Johansson, Örjan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Lindegren, David
    Luleå tekniska universitet.
    Analysis of everyday sounds which are extremely annoying for children with autism2008Ingår i: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 123, nr 5, s. 3299-Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Extreme sensitivity to noise is a problem that almost all autistic children suffer from. A sound that is extremely annoying does not need to be loud. However, the characteristics and temporal variations of these sounds are sparsely investigated. The aim of this study is to increase the knowledge about these extremely annoying sounds so they can be avoided by better design criteria for classrooms and venues like that. By interviewing teachers and parents a number of everyday sounds were identified and binaurally recorded. Examples are vacuum cleaners, ventilation noise, washing machines and pouring water. Detailed psychoacoustic analyses of this type of sounds were achieved by a listening test procedure in three parts. First 16 children composed different types of vacuum cleaner sounds trying to minimize annoyance in two different tests, a) keeping original sound pressure level. b) adjusting to acceptable loudness. In the second part, teachers working with autistic children performed a listening test to evaluate some of the composed sounds from part 1 and modified versions of them. The third part was performed by children to validate the results. The results showed that Roughness, Loudness and an index defined as High frequency tonality were the most important characteristics.

  • 18.
    Odelius, Johan
    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.
    The effect of binaural processing techniques on speech quality ratings of assistive listening devices in different room acoustics conditions2008Ingår i: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 123, nr 5, s. 3170-Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    External microphone systems, referred to as assistive listening devices (ALD), are used in classrooms for hearing impaired students. The objective is to investigate the effect of binaural processing techniques in different room acoustic conditions. A listening experiment was conducted with 10 normal hearing adults. Response variables were judgements of clarity, pleasantness, listening effort and overall speech quality. Design variables were binaural processing, room acoustics and ALD bandwidth. Stimuli were generated using the room acoustic modelling software CATT Acoustic. Three speech sources, two male voices and one female voice, were placed at a table in the centre of a room and one Brown noise source was placed in one corner of the room. Microphones were placed 0.5 m in front of each speech source. Target source was a random choice of one of the two male voices. The binaural processing was utilized by a simple HRTF filtering. Depending on the angle to the source from a fictitious listening position at the table, corresponding interaural time difference (ITD) and the interaural level difference (ILD) was applied to the signal. Stimuli were presented by loudspeakers using cross-talk cancellation. The hypothesis is that binaural processing will give a significant improvement in speech quality.

  • 19.
    Nykänen, Arne
    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.
    Design of product sound by blending of sound sources2007Ingår i: The 19th International Congress on Acoustics, ICA 2007 : Madrid: Acoustics for the 21st century / [ed] Antonio Calvo-Manzano, Madrid: Spanish Acoustical Society , 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    Product sound usually consists of a mix of several sources. Models for prediction of sound quality based on combinations of psychoacoustic metrics like loudness, sharpness and roughness have limitations when compound sounds are analysed. When a compound sound is divided into separable sources through auditory streaming such models fail. The character of each source is given by physical properties. The character is usually hard to change without complete redesign of the product. The quality of the final product sound is determined by the mix of sound sources. Efficient product sound design requires tools for recording or simulation of sources, realistic modelling of transfer functions from source to listener and tools for mixing the sources. With such tools a sound source can be auralised as part of sound environments. Recordings of sound sources in a car were used to get source information. The sound from each source was filtered through idealised transfer functions, mixed and reproduced in a 5.1 surround sound studio. The resulting sound was evaluated through listening tests. This approach was shown to be a powerful tool for evaluation of the effect of auditory streaming on subjective judgments of compound product sound.

  • 20.
    Frenne, Nicklas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Acoustic time histories from vibrating surfaces of a diesel engine2006Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 67, nr 3, s. 230-248Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An experiment on a diesel engine provides for validation of a method that retrieves source strength spectra, source strength time histories and sound pressure time histories of the engine's complex partial sources. The method is based on empirical transfer function measurements and inverse matrix calculations briefly described in the article. Different simplifying source models were selected by comparison of calculated and measured auto spectra. The results show: (1) indication of time efficient measurements of source strength spectra, (2) the importance of correct source models in the case of separated source strength time histories, and (3) spectra of separated sound pressure time histories. Listening tests reported that it is possible to detect well differentiated sounds of the partial sources as a result of the method.

  • 21.
    Odelius, Johan
    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.
    Ågren, Anders
    Effects on speech intelligibility using a binaural assistive listening device2006Ingår i: Proceedings of the Baltic-Nordic Acoustic Meeting: BNAM, 2006Konferensbidrag (Refereegranskat)
  • 22.
    Johansson, Örjan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Liljergren, M.
    Sound localisation using hearing protectors2006Ingår i: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 92, nr suppl 1Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Using a hearing protective device, feedback from the surroundings is of importance. Three aspects to be considered is the ability to communicate orally, the possibility to localize sound sources and to obtain a natural impression of the sounding environment. This could only be achieved by using a protective device that allow acoustic feedback, typically by a pair of microphones attached to the cup of each ear. The microphone signal is fed via an amplifier and an electronic compressor, that limit the amplitude of the signal fed to the loud speakers inside the cups. Typical problems with this type of solution are that the signals received by the two ears are distorted so much that sound localisation is difficult and that the sound is perceived unnatural. The objective of the project is to optimise the cup geometry especially where the microphones are mounted, and by that improve sound localisation and minimise the amplification of non-important weak sounds like the foot step of the user

  • 23.
    Odelius, Johan
    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.
    Ågren, Anders
    Communication quality for students with hearing impairment: a study evaluating speech intelligibility and annoyance2005Ingår i: Proceedings Forum Acusticum, Scientific society for optics, acoustics, motion picture and theater technology , 2005, s. 2709-2714Konferensbidrag (Refereegranskat)
    Abstract [en]

    New pedagogical views on assistive listening devices have enlightened the technology's impact on communication patterns among students with a hearing impairment. The objective of this study was to find methods to evaluate assistive listening devices supporting a more dialogue-oriented and participatory learning environment. With this approach a three-dimensional communication quality definition was proposed. The dimensions are: 1) Speech intelligibility 2) Ambient sounds; annoyance and feeling of presence 3) Parameters concerning the students' performance given the aim and task of the pedagogical situation. In this experiment dimensions 1 and 2 were evaluated, where dimension 2 concerned annoyance. Speech intelligibility was assessed using just-follow-conversation (JFC) tasks performed by normal hearing subjects. The task consisted of adjusting the level of a masker until the listener felt he or she just could understand what was being said. In conjunction with the JFC task, the subjects were asked to estimate the annoyance of the masking signal on an eleven-point scale. The speech and masking signals were filtered by impulse responses generated in a room acoustic model. Design variables were: A) Room acoustic model; two acoustic properties B) Distance between speech source and microphone; 0.75 m or 1.5 m C) Noise masker; speech-spectrum random noise or structure-borne noise D) Microphone directivity; omni-directional or delay-and-sum beamformer E) Amplifier; linear or compression.

  • 24.
    Nykänen, Arne
    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.
    Lundberg, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Berg, Jan
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Medier ljudteknik och upplevelseproduktion och teater.
    Perceptual and acoustical dimensions of saxophone sound2005Ingår i: Forum Acusticum Budapest 2005, 4th European Congress on Acoustics: 29 August - 2 September 2005, Budapest, Hungary, 2005, s. 519-524Konferensbidrag (Refereegranskat)
    Abstract [en]

    Specifications of product sound qualities may contain both perceptual and acoustical descriptions. The perceptual descriptions are most helpful when they contain adequate detail and utilises understandable wording. To facilitate the product design process the descriptions should also be interpretable as acoustical quantities. The objectives of the study reported upon here were to investigate how musicians use verbal descriptions of sound and to interpret these descriptions in terms of commonly used acoustical quantities. Musicians' use of verbal descriptions of saxophone sound was investigated through interviews. The most frequently used words were evaluated through listening tests. The subjects were asked to judge how well the words described the timbre of test sounds. To find the most significant perceptual dimensions for the test sounds Principal Component Analysis was used. Four significant dimensions were found and described by 9 words. To interpret the perceptual dimensions in terms of physically measurable indices, models for how acoustical quantities relate to the perceptual dimensions were developed. Dimension 1 was described by full-toned/warm/soft. The psycho-acoustical quantity sharpness correlated negatively with this dimension. Dimension 2 was described by the term [o]-like. Sharpness and specific roughness (9-11 Bark) correlated negatively with this dimension. Dimension 3 was described by sharp/keen/rough. Sharpness and roughness correlated with this dimension. Dimension 4 was described by the term [e]-like. No model for prediction of this dimension was found. To validate the models the effect of a changed design of the tone holes of a saxophone was predicted with the model and validated with new listening tests.

  • 25.
    Jönsson, P.
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Prediction of vehicle discomfort from transient vibrations2005Ingår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 282, nr 3-5, s. 1043-1064Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vehicle manufacturers are continuously seeking to improve vibration comfort. In this paper, subjective responses from transient vibrations in a forklift were analyzed on the basis of ISO 2631-1 and a number of additional variables. The objectives were to define: the effect of different operating conditions and appropriate background variables of subjects on perceived motions; the development of model that describes perceived discomfort as a function of measured vibrations; and important frequencies for prediction of vibration discomfort. The experiment was based on 12 different operating conditions defined by the variables: vehicle speed, obstacle height and load conditions. Eleven professional drivers participated and their responses of overall discomfort were defined by a vector sum of three perceived motions: shaking, for-aft and up-down motions. The evaluation method, maximum transient vibration value as defined in ISO 2631-1 was found to be adequate in predicting vibration discomfort during a four second transient vibration exposure. By analysis of narrow frequency band spectra of vibrations several explanations for the test results are discussed. The best results were obtained using a prediction model based on accelerations in -octave bands of pitch vibrations.

  • 26.
    Johnsson, Roger
    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.
    Sensitivity analysis of transfer function estimation in inverse methods2005Ingår i: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, nr Suppl 1, s. S16-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Summary form only given. A complex sound source consists of several partial sound sources that all contribute to the total sound pressure. A method to separate these partial sound sources into separate time histories is based on inverse filtering of reciprocally measured transfer functions. The transfer functions are measured reciprocally between a number of fictitious monopoles on each partial source and measurement points distributed around the sound source. The method is divided into 5 steps: recording of sound pressure signals, measurement of transfer function, calculation of source strength matrix, calculation of filters and filtering of the recorded sound pressure signals. Correct estimations of the transfer functions are critical for inverse methods to work satisfactory. Normally the transfer functions in this case of studies are calculated as H1 because of the noise contribution to the responses. However, it has been suggested that inverse methods could benefit of using H2 instead. The objective of this investigation is to analyze the effect of selecting either H1 or H2 for the calculation of the transfer functions in case of auralization of separated time histories. For the experiments a complex sound source consisting of two separate cylinder heads with valve covers have been used. Each cylinder head with valve cover was treated as a partial source. The two partial sources were excited with two uncorrelated signals that could be controlled individually. By that, listening tests could be used to verify the authenticity of the separated source signals depending of the transfer functions were estimated as H1 or H2

  • 27.
    Nykänen, Arne
    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.
    Development of a language for specifying saxophone timbre2003Ingår i: Proceedings of SMAC 03: Stockholm Music Acoustics Conference, August 6-9, 2003. / [ed] Roberto Bresin, Stockholm: Kungl. Tekniska Högskolan , 2003, Vol. 2, s. 647-650Konferensbidrag (Refereegranskat)
  • 28.
    Trapenskas, Donatas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Noise annoyance evaluation in a steel plant using binaural technology2003Ingår i: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 89, nr 5, s. 888-99Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This investigation had two goals: first was the evaluation of noise annoyance in seven control rooms based on listening tests and psychoacoustical parameters; second was the comparison of four hearing protective devices in terms of noise annoyance while exposed to loud sounds from a steel plant. Binaural recording technique was used for recording and playback of the sound signals. A total of 48 subjects participated in the first experiment and 8 subjects participated in the second experiment. They evaluated noise annoyance on an 11 point scale. In the second experiment four hearing protective devices were tested: two types of ear cups, slow-recovery foam ear plugs and custom modeled ear plugs. Loudness and roughness were the most significant contributors to noise annoyance in control rooms. Interaction between loudness, sharpness, roughness, and tonality were statistically significant. Noise annoyance with ear cups was lower than with ear plugs. However, this effect was dependent on gender. Ear cups reduced noise annoyance for male subjects more, than for female subjects

  • 29. Johansson, Örjan
    et al.
    Johnsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Sound intensity measurements of transient noise in presence of extraneous noise2003Ingår i: Inter-Noise 2003, the 32nd International Congress and Exposition on Noise Control Engineering: August 25 - 28, 2003, International Convention Center Jeju, Seogwipo, Korea, Seoul: International institute of noise control engineering , 2003Konferensbidrag (Refereegranskat)
  • 30.
    Frenne, N.
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Sound source characterisation and transfer path analysis with time histories2003Ingår i: International Journal for Transformative Research, ISSN 1027-5851, E-ISSN 2360-7866, Vol. 8, nr 3, s. 167-175Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The article describes a method to separate time histories of partial sound sources. The goal is to develop a noise control engineering tool for use in sound quality improvement applications. Contributions from partial sound sources are identified. The partial sound sources may be ranked for the purpose of creating a better mixture of sound in selected listening positions. The strategy is to reproduce time histories of sources of importance. The method described includes experimental and calculation parts. The experimental part consists of the recording of sound pressure time signals, reciprocal measurement of frequency response functions, and source strength estimation of partial sound sources. The calculation part comprises calculation of the cross-spectral matrix of source strength, calculation of filters, and filtered sound pressure recording to obtain time signals of the individual sources. Usually the contribution from partial sources is impossible to record directly. In this laboratory experiment, such control was possible. The laboratory experiment shows that the method described makes it possible to produce informative separation of time histories of partial sound sources. The effects of the errors in the calculated time histories are audible but not pronounced

  • 31.
    Frenne, Nicklas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Sound Source Characterisation and Transfer Path Analysis with Time Histories2003Ingår i: International Journal of Acoustics and Vibration, ISSN 1027-5851, Vol. 8, nr 3, s. 167-175Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The article describes a method to separate time histories of partial sound sources. The goal is to develop a noise control engineering tool for use in sound quality improvement applications. Contributions from partial sound sources are identified. The partial sound sources may be ranked for the purpose of creating a better mixture of sound in selected listening positions. The strategy is to reproduce time histories of sources of importance. The method described includes experimental and calculation parts. The experimental part consists of the recording of sound pressure time signals, reciprocal measurement of frequency response functions, and source strength esti- mation of partial sound sources. The calculation part comprises calculation of the cross-spectral matrix of source strength, calculation of filters, and filtered sound pressure recording to obtain time signals of the individual sources. Usually the contribution from partial sources is impossible to record directly. In this laboratory experi- ment, such control was possible. The laboratory experiment shows that the method described makes it possible to produce informative separation of time histories of partial sound sources. The effects of the errors in the cal- culated time histories are audible but not pronounced.

  • 32.
    Wijaya, A.R.
    et al.
    Luleå tekniska universitet.
    Jönsson, P.
    Luleå tekniska universitet.
    Johansson, Örjan
    The effect of seat design on vibration comfort2003Ingår i: International Journal of Occupational Safety and Ergonomics, ISSN 1080-3548, E-ISSN 2376-9130, Vol. 9, nr 2, s. 193-210Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A field study was done to evaluate different seat designs in the aspect of minimizing vibration transmission and reducing the level of discomfort experienced by drivers subjected to transient vibration. Two seat designs (sliding or fixed in the horizontal direction) were compared in an experiment based on variation of sitting posture, speed, and type of obstacle. The comparison was done by assessing discomfort and perceived motion and by vibration measurement. Ten professional drivers were used as participants. Maximum Transient Vibration Value and Vibration Dose Value were used in the evaluation. The results showed that a sliding seat is superior in attenuating vibration containing transient vibration in the horizontal direction. It was also perceived as giving less overall and low back discomfort compared to a fixed seat.

  • 33.
    Frenne, Nicklas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Time histories from partial sound sources and generalised cross validation2003Ingår i: Proceedings of the 10th International Congress on Sound and Vibration (ICSV10): Stockholm, July 7-10, 2003 / [ed] A. Nilsson; H. Bodén, International Institute of Acoustics and Vibration , 2003, s. 3476-3486Konferensbidrag (Refereegranskat)
  • 34.
    Jonsson, Peter
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Johansson, Örjan
    Parameters of importance in the prediction of vibration comfort2002Ingår i: Proceedings of Inter-Noise 2002, the 2002 International Congress and Exposition on Noise Control Engineering [and] additional proceedings: SQS 2002, Dearborn, Michigan, USA, August 22, 2002 [and] additional information: technical activities of INCE/USA and International INCE, Dearborn, Mich: Institute of noise control engineering , 2002, s. 1078-1083Konferensbidrag (Refereegranskat)
  • 35.
    Wijaya, Andi Rahadiyan
    et al.
    Luleå tekniska universitet.
    Johnsson, Peter
    Luleå tekniska universitet.
    Johansson, Örjan
    Predicting discomfort based on multi-axis vibration2002Ingår i: Proceedings of Inter-Noise 2002, the 2002 International Congress and Exposition on Noise Control Engineering [and] additional proceedings: SQS 2002, Dearborn, Michigan, USA, August 22, 2002 [and] additional information: technical activities of INCE/USA and International INCE, Dearborn, Mich: Institute of noise control engineering , 2002, s. 1084-1089Konferensbidrag (Refereegranskat)
  • 36.
    Trapenskas, Donatas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Localization performance of binaurally recorded sounds with and without training2001Ingår i: International Journal of Industrial Ergonomics, ISSN 0169-8141, E-ISSN 1872-8219, Vol. 27, nr 6, s. 405-410Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of the problems associated with listening to binaurally recorded sound events is localization confusions. The main objective of this investigation was to find out whether a short training session prior to listening to binaural recordings through headphones would facilitate correct spatial perception of the sound field. Focus was on the localization of the sound stimuli in median plane. Sound signals were recorded with an artificial head in three different conditions namely, anechoic, highly reverberant and moderately reverberant. Fourteen subjects participated in the listening tests. All subjects were required to localize all virtual sound stimuli under two different conditions. The first condition had a short training session binaurally recorded in the same environments as preceeding sound stimuli, and only sound stimuli recorded in the same environment were presented. The second condition did not have a training session, and sound stimuli recorded in different environments were presented. Results showed that a short training session prior to listening to binaurally recorded sounds through headphones was useful as it facilitated localization performance. The biggest effect was in reduced amount of sounds perceived inside the head. It was most pronounced for sound stimuli recorded in anechoic environment.

  • 37.
    Tinnsten, M.
    et al.
    Luleå tekniska universitet.
    Jonsson, Maria
    Johansson, Örjan
    Prediction and verification of acoustic radiation2001Ingår i: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 87, nr 1, s. 117-127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper the boundary element method (BEM) is used to determine acoustic-related quantities in open domains from vibrating structures. Two different types of structures have been analysed, a sphere and an engine transmission cover. The analysed acoustical quantities are pressure amplitude and pressure and intensity amplitude respectively. The numerical results were compared with the analytical and experimental results. In both cases, the sphere and the transmission cover, the input to the BEM program is the normal velocity of the structure surface. The analysed frequency range was in the case of the sphere 100–5000 Hz and a good agreement between numerical and analytical results was obtained up to frequency 3500 Hz. In the engine transmission cover case, the analysed frequency range was 434–3552 Hz with an overall good agreement between numerical and experimental results in the frequency range of 644–1848 Hz.

  • 38.
    Frenne, Nicklas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Calculation of time histories from a subdivided sound2000Ingår i: Proceedings: Inter.Noise 2000 : August 27 - 30, 2000, Nice, France / [ed] Didier Cassereau, Paris: SFA , 2000, s. 2125-2130Konferensbidrag (Refereegranskat)
  • 39.
    Jönsson, P.
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Discomfort from transient motions2000Ingår i: Proceedings 8th European Conference of ISTVS, International Society for Terrain-Vehicle Systems , 2000, s. 195-202Konferensbidrag (Refereegranskat)
  • 40. Johansson, Örjan
    et al.
    Jönsson, Peter
    Luleå tekniska universitet.
    Discomfort from transient whole body vibrations2000Ingår i: Proceedings of the 7th international congress on sound and vibration ICSV-7, International Institute of Acoustics and Vibration , 2000Konferensbidrag (Refereegranskat)
  • 41. Johansson, Örjan
    et al.
    Jönsson, Peter
    Luleå tekniska universitet.
    Discomfort from transient whole body vibrations2000Ingår i: SVIB vibrationsnytt, ISSN 0281-6830, Vol. 18, nr 3Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 42. Johansson, Örjan
    Rapid measurements of acoustic intensity vector fields2000Ingår i: Proceedings of the 7th international congress on sound and vibration ISCV-7, International Institute of Acoustics and Vibration , 2000Konferensbidrag (Refereegranskat)
  • 43.
    Trapenskas, Donatas
    et al.
    Luleå tekniska universitet.
    Frenne, Nicklas
    Luleå tekniska universitet.
    Johansson, Örjan
    Relationship between HRFT's and anthropometric data2000Ingår i: Proceedings: Inter.Noise 2000 : August 27 - 30, 2000, Nice, France / [ed] Didier Cassereau, Paris: SFA , 2000, s. 4033-4037Konferensbidrag (Refereegranskat)
  • 44. Johansson, Örjan
    Relationship between psychoacoustic descriptors and annoyance: regarding sound in home environments2000Ingår i: Proceedings: Inter.Noise 2000 : August 27 - 30, 2000, Nice, France / [ed] Didier Cassereau, Paris: SFA , 2000, s. 4178-4186Konferensbidrag (Refereegranskat)
  • 45.
    Khan, M.S.
    et al.
    Luleå tekniska universitet.
    Trapenskas, Donatas
    Luleå tekniska universitet.
    Johansson, Örjan
    Technical note: Effects of different fuels on annoyance from diesel engine sounds2000Ingår i: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 48, nr 3, s. 102-106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Annoyance judgments of engine sounds under six different fuel conditions were investigated using forty subjects. An equal number of males and females participated in the listening test. Thirty stereophonic recorded sounds were randomly presented to the subjects through a pair of loudspeakers. All sounds were recorded in a hemi-anechoic room. The listening test was conducted using a sequential rating method known as the method of successive Intervals. Tests for effects of the different fuels were made on the basis of non-parametric statistics. Engine sounds for an ethanol fuel with 9% Beraid were rated as least annoying whereas engine sounds for a mixture of diesel and ethanol fuels were rated as most annoying, The differences In annoyance judgments for different fuels at the same engine running speed could not be predicted using the annoyance index developed in an earlier study based on loudness, sharpness and harmonic ratio.

  • 46. Johansson, Örjan
    Acoustic measurements for assessments of noise annoyance in work places1999Ingår i: Proceedings of the 10th year anniversary of M. Sc. ergonomics: International conference, Luleå, Sweden, 29-30 October 1999 / [ed] John Abeysekera; Emma-Christin Lönnroth; D. Paul T. Piamonte; Houshang Shahnavaz, Luleå: Luleå University of Technology. Department of Human Work Sciences. Division of Industrial Ergonomics , 1999, s. 85-91Konferensbidrag (Refereegranskat)
  • 47. Johansson, Örjan
    Akustiska mätmetoder och mätstorheter för bedömning av bullerstörningsrisk1999Ingår i: Störande buller: Kunskapsöversikt för kriteriedokumentation, Solna: Arbetslivsinstitutet , 1999, s. 3-18Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 48. Johansson, Örjan
    et al.
    Trapenskas, Donatas
    Luleå tekniska universitet.
    Appropriate sound quality descriptors1999Ingår i: Sixth International Congress on Sound and Vibration: proceedings, Technical University of Denmark, Lyngby, Denmark, 5-8 July 1999 / [ed] Finn Jacobsen, Lyngby: Technical university of Denmark, Dep. of acoustic technology , 1999Konferensbidrag (Refereegranskat)
  • 49.
    Frenne, Nicklas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Assessing the sound of different transfer paths from a subdivided sound source1999Ingår i: Sixth International Congress on Sound and Vibration: , Technical University of Denmark, Lyngby, Denmark, 5-8 July 1999 / [ed] Finn Jacobsen, Lyngby: Technical university of Denmark, Dep. of acoustic technology , 1999Konferensbidrag (Refereegranskat)
  • 50.
    Trapenskas, Donatas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Effects of training on the correct spatial perception of binaurally recorded sounds1999Ingår i: Sixth International Congress on Sound and Vibration: proceedings, Technical University of Denmark, Lyngby, Denmark, 5-8 July 1999 / [ed] Finn Jacobsen, Lyngby: Technical university of Denmark, Dep. of acoustic technology , 1999Konferensbidrag (Refereegranskat)
12 1 - 50 av 85
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