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  • 1.
    Frenne, N.
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Sound source characterisation and transfer path analysis with time histories2003In: International Journal for Transformative Research, ISSN 1027-5851, E-ISSN 2360-7866, Vol. 8, no 3, p. 167-175Article in journal (Refereed)
    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

  • 2.
    Frenne, Nicklas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Acoustic time histories from vibrating surfaces of a diesel engine2006In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 67, no 3, p. 230-248Article in journal (Refereed)
    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.

  • 3.
    Frenne, Nicklas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Assessing the sound of different transfer paths from a subdivided sound source1999In: 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 , 1999Conference paper (Refereed)
  • 4.
    Frenne, Nicklas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Calculation of time histories from a subdivided sound2000In: Proceedings: Inter.Noise 2000 : August 27 - 30, 2000, Nice, France / [ed] Didier Cassereau, Paris: SFA , 2000, p. 2125-2130Conference paper (Refereed)
  • 5.
    Frenne, Nicklas
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Time histories from partial sound sources and generalised cross validation2003In: 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, p. 3476-3486Conference paper (Refereed)
  • 6. Johansson, Örjan
    Acoustic measurements for assessments of noise annoyance in work places1999In: 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, p. 85-91Conference paper (Refereed)
  • 7. Johansson, Örjan
    Akustiska mätmetoder och mätstorheter för bedömning av bullerstörningsrisk1999In: Störande buller: Kunskapsöversikt för kriteriedokumentation, Solna: Arbetslivsinstitutet , 1999, p. 3-18Chapter in book (Other academic)
  • 8.
    Johansson, Örjan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Application of the sound method for characterisation of engine noise sources1994Licentiate thesis, comprehensive summary (Other academic)
  • 9.
    Johansson, Örjan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Energieffektivisering genom flödesexciterad, resonansförstärkt och ultraljudskontrollerad kavitation: Delprojekt inom Mekmassainitiativet för energieffektivitet (E2MPi)2016Report (Other academic)
    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.

  • 10.
    Johansson, Örjan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Experimental and multivariate analysis methods for sound quality evaluation of diesel engines1996Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Noise control and sound quality analysis are important, since noise has been registered to be a predominant factor in stress and a source of great annoyance. Traffic noise is a problem and a major part of this noise comes from heavy vehicles. The only legislative requirement for heavy-duty trucks regarding noise emissions, is that the noise level does not exceed an Aweighted sound pressure level of 80 dB. The specification of an A-weighted sound pressure level is, however, not an adequate description of psychoacoustic annoyance and therefore work towards defining a better description of loudness is one of the principal fields of acoustics today. Sound radiation from trucks is speed-related. At medium and high speeds, the overall noise level is comprised mainly of the tyre noise, whereas at low speed and during acceleration, exhaust noise and noise from the engine and transmission structure are predominant. In front of the truck, the noise from the engine and especially that from the timing transmission cover, the torsional damper and the oil sump, comprises a greater proportion of the total noise. The aim of sound quality analysis of diesel engines is to find cost-efficient methods of reducing sound radiation and of changing the character of the sound in order to minimise annoyance. This thesis concerns the development of experimental methods for analysing the sound quality of diesel engines, and focuses on measurement of acoustic intensity, multivariate data analysis, structural modification and subjective assessment of engine noise. The applicability of the FFT-based sound intensity method is evaluated. It is found that the intensity measurements may be influenced by high reactivity, interference due to partlycoherent sources, difficulties in performing the spatial average, real-time limitations and engine speed variations. Scanning the intensity probe, preferably by a robot, is necessary when measuring within narrow bands to avoid interference problems. Scanning achieves more reliable estimates of sound power and intensity vectors. Experimental design and the multivariate techniques, principal components analysis (PCA) and partial least squares (PLS) were utilised to facilitate interpretation of intensity measurements. The results show that PCA and PLS enable independent phenomena in the sound field to be extracted and which can thereby be visualised by principal spectra and principal radiating patterns. The characteristics of sound radiation are determined by designed experiments, sound intensity measurements and operational deflection shape estimations. These methods enable the effects on sound radiation of structure modifications to be predicted. An annoyance index for in-line 6-cylinder diesel engines in stationary running conditions was developed using multivariate statistics. The index is based on engine sounds resulting from structure modifications and changes in fuel. The annoyance level was measured during listening tests of sound stimuli recorded in stereo and reproduced by loudspeakers under anechoic conditions. The different sound stimuli were ranked using paired comparisons or the method of successive intervals. It was found that 94% of the variance of annoyance can be explained by a model based on loudness (Sone), sharpness (Acum) and harmonic ratio (rumble). Impulsiveness, roughness and tonality were other important criteria used in the study and which were found to have a relationship with specific speed ranges. The annoyance was minimised by an increase in stiffness in the lower part of the engine achieved by using a ladder frame in combination with a bearing beam.

  • 11. Johansson, Örjan
    Multivariatanalys av ljudintensitetsmätningar i 3D1997In: SVIB Vibrationsforskningsdag, 1997Conference paper (Refereed)
  • 12. Johansson, Örjan
    Multivariate analysis of FFT based Intensity measurements1996In: Proceedings of Forum acusticum 1996, the 1st convention of the EAA - European Acoustics Association, 1996Conference paper (Refereed)
  • 13. Johansson, Örjan
    Principal component analysis of FFT-based 3D intensity measurements1997In: Help quiet the world for a higher quality life: proceedings / [ed] Fülöp Augusztinovicz, Budapest: Scientific society for optics, acoustics, motion picture and theater technology, OPAKFI , 1997, p. 851-854Conference paper (Refereed)
  • 14. Johansson, Örjan
    Rapid measurements of acoustic intensity vector fields2000In: Proceedings of the 7th international congress on sound and vibration ISCV-7, International Institute of Acoustics and Vibration , 2000Conference paper (Refereed)
  • 15. Johansson, Örjan
    Relationship between psychoacoustic descriptors and annoyance: regarding sound in home environments2000In: Proceedings: Inter.Noise 2000 : August 27 - 30, 2000, Nice, France / [ed] Didier Cassereau, Paris: SFA , 2000, p. 4178-4186Conference paper (Refereed)
  • 16. Johansson, Örjan
    Sound intensity vector fields in relation to different reference signals1997In: Fifth International Congress on Sound and vibration: proceedings, University of Adelaide, South Asutralia, December 15-18, 1997 / [ed] Colin H. Hansen ; George Vokalek, St. Petersburgh, Russia: International Institute of Acoustics and Vibration , 1997Conference paper (Refereed)
  • 17. Johansson, Örjan
    The applicability of FFT based sound intensity technique for engine measurements1994In: Proceedings of Nordic acoustical meeting, NAM 94 / [ed] Henrik S. Olesen, Aarhus: Danish technological institute , 1994Conference paper (Refereed)
  • 18. Johansson, Örjan
    et al.
    Cui, L.
    Luleå tekniska universitet.
    Tonality modelling on the basis of spectral and virtual pitch of complex sounds using multivariate analysis.1998In: Designing for silence: prediction, measurement and evaluation of noise and vibration; proceedings / [ed] Hugo Fastl, Oldenburg: German Acoustical Society (DEGA), Univ. of Oldenburg, Physics/Acoustics, , 1998Conference paper (Refereed)
  • 19. Johansson, Örjan
    et al.
    Johnsson, Roger
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Sound intensity measurements of transient noise in presence of extraneous noise2003In: 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 , 2003Conference paper (Refereed)
  • 20. Johansson, Örjan
    et al.
    Jönsson, Peter
    Luleå tekniska universitet.
    Discomfort from transient whole body vibrations2000In: Proceedings of the 7th international congress on sound and vibration ICSV-7, International Institute of Acoustics and Vibration , 2000Conference paper (Refereed)
  • 21. Johansson, Örjan
    et al.
    Jönsson, Peter
    Luleå tekniska universitet.
    Discomfort from transient whole body vibrations2000In: SVIB vibrationsnytt, ISSN 0281-6830, Vol. 18, no 3Article in journal (Other (popular science, discussion, etc.))
  • 22. Johansson, Örjan
    et al.
    Kahn, M.S.
    Luleå tekniska universitet.
    Ågren, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Sound quality assessment of a diesel engine due to structure modifications1996In: Noise control - the next 25 years: proceedings, St Albans: Institute of Acoustics , 1996Conference paper (Refereed)
  • 23.
    Johansson, Örjan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Liljergren, M.
    Sound localisation using hearing protectors2006In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 92, no suppl 1Article in journal (Other academic)
    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

  • 24.
    Johansson, Örjan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lindegren, David
    Luleå tekniska universitet.
    Analysis of everyday sounds which are extremely annoying for children with autism2008In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 123, no 5, p. 3299-Article in journal (Other academic)
    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.

  • 25.
    Johansson, Örjan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Pamidi, Taraka Rama Krishna
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Design of high-intensity ultrasound reactor2017In: IEEE International Ultrasonics Symposium, IUS, Piscataway, NJ: IEEE Computer Society, 2017, article id 8092948Conference paper (Refereed)
    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

  • 26.
    Johansson, Örjan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Pamidi, Taraka
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Khoshkhoo, Mohammad
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Sustainable and energy efficient leaching of tungsten(W) by ultrasound controlled cavitation2017Report (Other academic)
    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.

  • 27.
    Johansson, Örjan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Pamidi, Taraka Rama Krishna
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Design of a high-intensity ultrasound reactor2017Conference paper (Refereed)
    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.

  • 28.
    Johansson, Örjan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Pamidi, Taraka Rama Krishna
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Design of a high-intensity ultrasound reactor2017In: IEEE International Ultrasonics Symposium, IUS, Piscataway, NJ: IEEE Computer Society, 2017, article id 8091660Conference paper (Refereed)
    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

  • 29.
    Johansson, Örjan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Schönfeld, Stephan
    ÅF-Infrastructure AB.
    Lindforss, Daniel
    ÅF-Infrastructure AB.
    Sound sketch procedure for auralization of the interior sound of a high speed train2012In: 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 , 2012Conference paper (Other academic)
  • 30. Johansson, Örjan
    et al.
    Trapenskas, Donatas
    Luleå tekniska universitet.
    Appropriate sound quality descriptors1999In: 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 , 1999Conference paper (Refereed)
  • 31. Johansson, Örjan
    et al.
    Trapenskas, Donatas
    Luleå tekniska universitet.
    Localization performance of binaurally recorded sounds with and without training1999In: 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, p. 92-97Conference paper (Refereed)
  • 32. Johansson, Örjan
    et al.
    Ågren, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    A study of the interaction effects between the torsional vibration damper and engine structure by gated measurements1994In: Noise - quantity and quality: proceedings / The 1994 International Congress on Noise Control Engineering, Inter-Noise 94 ; Yokohama, Japan, August 29 - 31, 1994, Poughkeepsie, NY: Noise control foundation , 1994, p. 395-398Conference paper (Refereed)
  • 33. Johansson, Örjan
    et al.
    Ågren, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Noise radiation from a torsional vibration damper in a diesel engine1993In: People versus noise: proceedings of the 1993 International congress on noise control engineering, Inter-Noise 93 / [ed] Pierre Chapelle; Gerrit Vermeir, Poughkeepsie, NY: Noise control foundation , 1993Conference paper (Refereed)
  • 34. Johansson, Örjan
    et al.
    Ågren, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Noise radiation from the torsional damper in a diesel engine: an investigation of the interaction effect between the torsional damper and the timing cover1992Report (Other academic)
  • 35. Johansson, Örjan
    et al.
    Ågren, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    The use statistical methods to predict the noise radiation from a torsional vibration damper in a diesel engine1993Report (Other academic)
  • 36. Johansson, Örjan
    et al.
    Ågren, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Lindberg, W.
    Luleå tekniska universitet.
    Principal components and partial least squares modelling of sound intensity measurements1995In: Proceedings of the 15th international congress on acoustics: Trondheim, Norway, 26-30 June 1995, Trondheim: Tapir Akademisk Forlag, 1995Conference paper (Refereed)
  • 37. Johansson, Örjan
    et al.
    Ågren, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Sundbäck, Ulrik
    Luleå tekniska universitet.
    Klopotek, Manfred
    Luleå tekniska universitet.
    Source characterization of the lower front-end of a diesel engine1996In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 49, no 4, p. 383-404Article in journal (Refereed)
    Abstract [en]

    The lower front end of a diesel engine is a major noise source. Describing the source mechanisms of this area is problematic as it consists of a rotating torsional vibration damper in front of the timing transmission cover and the oil sump. This experimental study focuses on the acoustic interaction phenomena between the damper and the structure behind it. To describe the source mechanisms a test series of different modifications by conventional lead wrapping technique is performed. The vibration behaviour of each substructure is determined by operational deflection shape measurements and the source strength for each modification is determined by near-field sound intensity measurements. The results show the contributions from different substructures and describes the interference effects due to coherent radiation. It is concluded that the radiation is dominated by the timing transmission cover structure behind the damper. At some frequencies though, the torsional vibration damper in combination with the timing transmission cover behind it, causes the high radiation. This effect is mainly due

  • 38.
    Johnsson, Roger
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Johansson, Örjan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Sensitivity analysis of transfer function estimation in inverse methods2005In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, no Suppl 1, p. S16-Article in journal (Refereed)
    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

  • 39.
    Jonsson, Peter
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Johansson, Örjan
    Parameters of importance in the prediction of vibration comfort2002In: 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, p. 1078-1083Conference paper (Refereed)
  • 40.
    Jönsson, P.
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Discomfort from transient motions2000In: Proceedings 8th European Conference of ISTVS, International Society for Terrain-Vehicle Systems , 2000, p. 195-202Conference paper (Refereed)
  • 41.
    Jönsson, P.
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Prediction of vehicle discomfort from transient vibrations2005In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 282, no 3-5, p. 1043-1064Article in journal (Refereed)
    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.

  • 42.
    Kahn, M.S.
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Sundbäck, U.
    Luleå tekniska universitet.
    A comparison of annoyance response between ethanol and diesel engines1995In: item: Proceedings of INTER-NOISE 95, the 1995 International Congress on Noise Control Engineering : Newport Beach, California, USA [1995 July 10 - 12] / [ed] Robert J. Bernhard, Poughkeepsie, NY: Noise control foundation , 1995, p. 123-126Conference paper (Refereed)
  • 43.
    Kahn, M.S.
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Sundbäck, Ulrik
    Luleå tekniska universitet.
    A laboratory study of sound quality with artificicial head and stereophonic recordings in free field conditions1998In: Proceedings of the 1998 sound quality symposium: Ypsilanti, Michigan, 1998 April 09 / [ed] Patricia Davies, Washington, DC: Noise control foundation , 1998, p. 43-48Conference paper (Refereed)
  • 44.
    Kahn, M.S
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Sundbäck, Ulrik
    Luleå tekniska universitet.
    A study of repeatabillity in annoyance judgements for engine noise in free field conditions1998In: Proceedings of the 1998 sound quality symposium: Ypsilanti, Michigan, 1998 April 09 / [ed] Patricia Davies, Washington, DC: Noise control foundation , 1998, p. 49-54Conference paper (Refereed)
  • 45.
    Kahn, M.S.
    et al.
    Luleå tekniska universitet.
    Sundbäck, Ulrik
    Luleå tekniska universitet.
    Johansson, Örjan
    Evaluation of annoyance response to engine sounds using different rating methods1996In: Noise control - the next 25 years: proceedings, St Albans: Institute of Acoustics , 1996Conference paper (Refereed)
  • 46.
    Khan, M. Shafiquzzaman
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Lindberg, Walter
    Luleå tekniska universitet.
    Sundbäck, Ulrik
    Annoyance of idling diesel engine noise evaluated by multivariate analysis1995In: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 43, no 6, p. 197-207Article in journal (Refereed)
  • 47.
    Khan, M. Shafiquzzaman
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Sundbäck, Ulrik
    Luleå tekniska universitet.
    Development of an annoyance index for heavy-duty diesel engine noise using multivariate analysis1997In: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 45, no 4, p. 157-167Article in journal (Refereed)
  • 48.
    Khan, M. Shafiquzzaman
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Sundbäck, Ulrik
    Luleå tekniska universitet.
    Subjective annoyance response to diesel engine sound during idling conditions1996In: International Journal of Occupational Safety and Ergonomics, ISSN 1080-3548, E-ISSN 2376-9130, Vol. 2, no 1, p. 16-26Article in journal (Refereed)
    Abstract [en]

    Subjective annoyance response to diesel engine sound during idling conditions was evaluated by 80 participants. Eight different sound spectra were presented to the participants at a constant level of 80 dB(A) in a paired comparison procedure. Stereo recorded sound stimuli were played back through a pair of loudspeakers in an anechoic room. Four objective parameters of loudness, sharpness, impulsiveness, and roughness were found to be the determining factors that cause subjective annoyance. An annoyance prediction model for the test stimuli of an idling diesel engine was developed on the basis of these factors. The objective parameters and their interactions have a significant effect on the annoyance prediction model. The spectral distribution indicated by test participants to be pleasant can be used as a basis for appropriate modification of engine sound. A single microphone measurement in free field conditions can be used to estimate objective parameters for defining the cause of annoyance.

  • 49.
    Khan, M.S.
    et al.
    Luleå tekniska universitet.
    Johansson, Örjan
    Sundbäck, U.
    Luleå tekniska universitet.
    The use of loudspeakers for evaluating subjective annoyance parameters due to diesel engine noise1994In: Proceedings of Nordic Acoustical Meeting - [NAM 94] / [ed] Henrik S. Olesen, Aarhus: Danish technological institute , 1994Conference paper (Refereed)
  • 50.
    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 sounds2000In: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 48, no 3, p. 102-106Article in journal (Refereed)
    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.

12 1 - 50 of 80
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