Sound Quality Evaluation and Optimization for Interior Noise of Rail Vehicle
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A procedure for sound filed simulation, sound quality (SQ) evaluation, and optimization of interior noise of a rail vehicle is investigated in this paper. Firstly, some interior noises are measured on site when the subway is running in tunnel at a speed of 60 km/h. The sound pressure levels (SPLs), loudness, sharpness, and roughness of the measured noise are analyzed. A finite element model for acoustical simulation of the carriage is established by using the Actran software. The accuracy and feasibility of the finite model are verified by comparing the psychoacoustical parameters from the simulations and measurements. By using orthogonal experimental design, finally, the best optimization scheme is put forward, which obtained a sound quality improvement with a 4.81 dB decrease in SPL and a 1.07 sone reduction in loudness. The proposed optimization scheme may be extended to other vehicles for improving interior acoustic environment.Keywords:
Sound Quality
To increase cabin comfort, not only decreasing sound pressure level but also improving the sound quality is essential. In addition, when the sound quality of the vehicle matches with the exterior design, the sound is considered to be perceived more attractive. In this study, to investigate the relationship between the perceptions of the sound and the exterior design, the loudness of acceleration sounds were evaluated with vehicle exterior images. In the loudness evaluation test, 10 acceleration sounds and 10 exterior images were prepared and half of the images were luxury vehicle images and the others were sporty vehicle images. The experimental subject evaluated the loudness of presented sound with the luxury or sporty vehicle exterior image. Twenty one male subjects participated in the test. Eleven of them drove vehicles frequently and the others were infrequently. As a result, frequently driving subjects felt the acceleration sound louder by having luxury vehicle impression. In contrast, infrequently driving subjects felt the sound softer by having the same vehicle impression. Consequently, it was clarified that perceived loudness was influenced by vehicle exterior design, and the tendency was changed depending on the driving frequency.
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In Japan, Lden is currently used as an evaluation index for aircraft noise. It is based on the A-weighted sound pressure. It evaluates differences in noise loudness, but it does not necessarily take into account differences due to changes in sound quality. Over the past several decades, single event of aircraft noise has been significantly reduced. As a result, we have experienced a change from the "noisy" sound quality of the old generation jets to the "soft" sound quality of the recent aircrafts. Has the sound quality really improved, and has its improvement been evaluated? On the other hand, since the 2000's, we have sometimes experienced hearing the extraordinary tonal sounds from landing aircraft. It has the characteristics of pure tonal tone with 250-500 Hz and has a short duration and a prominent level fluctuation. Doessuch a sudden tonality change, which is also negatively perceived, not affect the evaluation? This paper describes the results of trial calculation in order to examine the possibility of evaluating aircraft noise considering its sound quality, based on several indices such as EPNL, loudness, sharpness, and Tonal Audibility (TA), in addition to the A-weighted noise (LAmax, LEA), and its comparative verification including differences in aircraft generations.
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Aircraft noise
Tone (literature)
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When exploring sound quality, often a high correlation between pleasantness and loudness can be observed. However, sometimes it is desirable to know to which extent other sound characteristics than loudness are responsible for a preference evaluation. In this respect multi-tone sounds with rich perceptual aspects are interesting test sounds. This talk will present a separate determination of preference and loudness by comparing a test sound of interest with a reference sound. Using an adaptive paired comparison the points of subjective equality (PSEs) for preference and loudness between test and reference sound are separately measured - "Which sound is louder?" and "Which sound do you prefer?" - by varying the test sound level in an adaptive staircase manner. The level changes affect both loudness and preference evaluation of the test sound. The results of these experiments are level differences ΔL between the test and the reference sound at which equal preference and equal loudness are reached between them. (Similar procedures have been employed to determine equal loudness contours.) It will be shown, with multitone sounds as examples, how this method reliably differentiates between loudness and preference.
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Tone (literature)
Preference test
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This paper studies the relationship between the subjective evaluation indexes and the objective physical parameters from interior noise of vehicle cabin. Four types of vehicle real-time noises were recorded at several running speeds and later being subjectively evaluated in the testing room by pair comparison method and semantic subdivided method. Meanwhile, the psychoacoustic parameters were extracted. According to the subjective test and evaluation, a psychoacoustic objective quantificational model based on sound quality such as partialness, luxury and motility was built by means of multiple regression method. The research results indicate that loudness and sharpness are primary parameters : while loudness and sharpness are lower, then partialness and luxury are better, when the loudness is louder, then motility is stronger.
Psychoacoustics
Sound Quality
Annoyance
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Loudness Scattering due to Vibro-Acoustic Model VariabilityThe use of numerical simulation in the design and evaluation of products performance is ever increasing.To a greater extent, such estimates are needed in an early design stage, when physical prototypes are not available.When dealing with vibro-acoustic models, known to be computationally expensive, a question remains, which is related to the accuracy of such models in view of the well-known variability inherent to the mass manufacturing production techniques.In addition, both the academia and industry have recently realized the importance of actually listening to a products sound, either by measurements or by virtual sound synthesis, in order to assess its performance.In this work, the scatter of significant parameter variations on a simplified vehicle vibro-acoustic model is calculated on loudness metrics using Monte Carlo analysis.The mapping from the system parameters to sound quality metric is performed by a fully-coupled vibro-acoustic finite element model.Different loudness metrics are used, including overall sound pressure level expressed in dB and Specific Loudness in Sones.Sound quality equivalent sources are used to excite this model and the sound pressure level at the driver's head position is acquired to be evaluated according to sound quality metrics.No significant variation has been perceived when evaluating the system using regular sound pressure level expressed in dB and dB(A).This happens because of the third-octave filters that average the results under some frequency bands.On the other hand, Zwicker Loudness presents important variations, arguably, due to the masking effects.
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Identification of vehicle booming sound and its objective evaluation using psychoacoustic parameters
Previous work revealed that booming sound quality is related to loudness and sharpness and that the booming index is developed by using the loudness and sharpness for a signal within the whole frequency range between 20 Hz and 20 kHz. In the present paper, the booming sound quality was found to be effectively related to the loudness at frequencies below 200 Hz; thus the booming index is updated by using the loudness of the signal filtered by the low pass filter at frequencies. The relationship between the booming index and sound metric is identified by an Artificial Neural Network (ANN).
Psychoacoustics
Sound Quality
SIGNAL (programming language)
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Octave band
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The sound of a door opening on a vehicle has a main influence on psychological comfort and affective satisfaction for the vehicle. This study aims to evaluate the auditory pleasantness of the door opening sound and to derive the sound parameters, which can optimize that pleasantness. Fourteen different door opening sounds were selected and recorded. Participants evaluated each recorded door opening sound with the designed questionnaire. Three main results were obtained. First, the questionnaire was developed to evaluate the auditory pleasantness of door opening sound based on five affective attributes: ‘loud’, ‘sharp’, ‘rough’, ‘clear’, and ‘satisfy’. These were selected through previous literature review and expert interviews. Second, ‘Loudness’, ‘sharpness’, ‘roughness’, ‘fluctuation strength’, and ‘tonality’ were selected as the psychoacoustic parameters. These parameters were found to be the important dimensions for the perception of door opening sound. Each affective attribute was related to psychoacoustic parameters by correlation analysis. Finally, the authors developed a model to predict subjective response to the door opening sound through regression analysis. In the incidence of ‘loud’, ‘sharp’, and ‘rough’, high R2 values were shown. Multiple regression was used to create a model to predict auditory pleasantness. The psychoacoustic parameter ‘loudness’ was shown to have a major effect on auditory pleasantness. The parameters ‘loudness’, ‘sharpness’, and ‘roughness’ were shown to affect the attributes of the door opening sound. The result of this study was an optimal model, created through psychoacoustic parameters, to predict the auditory pleasantness of door opening sounds.
Psychoacoustics
Sound Quality
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The noises in the driver's cab and the carriage of a high-speed train are measured respectively at different speeds on site.By using the linear sound pressure level,A-weighted sound pressure level and specific loudness,the spectrum characteristics of the measured interior noises at 330km/h are analyred and the dominant frequency ranges are identified.Objective evaluation of the measured interior noises are carried out in respect of the sound quality of loudness,sharpness,roughness and fluctuation strength based on the psycho-acoustical theory.The research results indicate as follows:Analysis of the specific loudness accurately characterizes the frequency components which induce changes in loudness to the feeling of human ears;The loudness of interior noises at all measure points enhances coutinuously with increasing of the train speed,especially in the cab,the front car of the train,Which is under intensified aerodynamic effect;Loudness assessment tells that the interior acoustic environment of the high speed train needs to be further improved to satisfy the requirements of passengers for acoustic comfort,especially in the cab and at the position of the centre plates of the carriage where appropriate measures should be taken to reduce vibration and noises.
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High speed train
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