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- Johansson, Örjan, et al.
(författare)
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Source characterization of the lower front-end of a diesel engine
- 1996
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Ingår i: Applied Acoustics. - 0003-682X .- 1872-910X. ; 49:4, s. 383-404
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Tidskriftsartikel (refereegranskat)abstract
- 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
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- Khan, M. Shafiquzzaman, et al.
(författare)
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Annoyance of idling diesel engine noise evaluated by multivariate analysis
- 1995
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Ingår i: Noise Control Engineering Journal. - : Institute of Noise Control Engineering (INCE). - 0736-2501 .- 2168-8710. ; 43:6, s. 197-207
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Tidskriftsartikel (refereegranskat)abstract
- Judgments of annoyance caused by the sound of an idling diesel engine were determined by 80 subjects. The diesel-engine sounds were recorded and the spectra were subsequently modified electronically to produce various test signals. The subjects listened to eight different sounds in a paired-comparison procedure. Each sound signal was presented to the subjects at a time-averaged A weighted sound level of 80 dB. Two different prediction models of the annoyance response were developed by use of principal component analysis and partial least-squares regression. A new descriptor, the 'ear resonance range,' was discovered as a result of employing these analysis methods. The first prediction model, based on psychoacoustic measures, utilized the ear resonance range along with loudness and kurtosis to predict the annoyance judgments of the test signals. The second model utilized critical-band sound-pressure levels as the basis for the annoyance predictions. Both models were confirmed by internal and external validations and gave good predictions. The critical-band sound-pressure-level prediction model may provide a better means than the psychoacoustic-measure model to evaluate options for minimizing the annoyance of the sound from an idling diesel engine.
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| 7. |
- Khan, M. Shafiquzzaman, et al.
(författare)
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Development of an annoyance index for heavy-duty diesel engine noise using multivariate analysis
- 1997
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Ingår i: Noise Control Engineering Journal. - : Institute of Noise Control Engineering (INCE). - 0736-2501 .- 2168-8710. ; 45:4, s. 157-167
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Tidskriftsartikel (refereegranskat)abstract
- Annoyance response to vehicle noise is commonly reported by many people in society. A need to improve the sound quality of vehicles is therefore apparent. The engine is one of the most predominant sources of vehicle noise causing annoyance. Judgments of annoyance due to engine noise were made by 160 subjects in five separate listening tests. An M-S (mid-side) stereo microphone was used to record engine sounds under idling and running conditions for listening Tests A-C, and E. For listening test D, two microphones were used to record engine sounds in stereo under idling conditions. All sound stimuli were presented to the subjects through a pair of loudspeakers in an anechoic room. One of the listening tests was conducted using a paired comparisons method and the other listening tests were conducted using a sequential rating method known as the method of successive intervals. A prediction model of annoyance response was developed by the use of principal component analysis and partial least-squares regression. In this case, all original annoyance scores for all five separate tests were transformed into a common annoyance scale. The prediction model was based on three psychoacoustic descriptors: loudness, sharpness, and harmonic ratio. The model was validated internally and also externally by three new sound stimuli. The prediction of annoyance for these three sounds was found to be consistent when judged by 20 additional subjects. The model gave good predictions of annoyance judgments for 6-cylinder in-line engine noise.
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| 8. |
- Khan, M. Shafiquzzaman, et al.
(författare)
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Subjective annoyance response to diesel engine sound during idling conditions
- 1996
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Ingår i: International Journal of Occupational Safety and Ergonomics. - : Informa UK Limited. - 1080-3548 .- 2376-9130. ; 2:1, s. 16-26
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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