The Design of Automotive Acoustic Environments: Using Subjective Methods to Improve Engine Sound Quality (original) (raw)
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IPA - A Subjective Assessment Method of Sound Quality of Car Sound Systems
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Journal of Traffic and Transportation Engineering, 2015
Vehicle sounds are important factors of customer satisfaction and have a decisive influence on the product automobile and its quality impression. It becomes more and more important to connect customer requirements and technical specifications to develop a vehicle sound with high quality. The turn indicator sound can be described as one sound, which gives the customer an important feedback of correct function performance and can be seen as one of the sounds, which play a role in the customer's perception of vehicle quality. In a laboratory experimental study, the question was investigated, how a turn indicator sound must be designed to be perceived as pleasant and high-quality. A multidimensional approach was chosen to combine subjective customer assessments, objective psychophysiological responses of the study participants and physical parameters of the sounds. In total, 15 different turn indicator sounds were assessed by 48 subjects. The study shows how the connection of subjective and objective parameters can support product development. The multi-dimensional approach helps to derive recommendations for action to improve the sound quality of the product automobile. Also, the study shows a possibility to involve the human factor in a highly technical environment.
Proceedings of the 9th …, 2008
This paper describes sound quality evaluations of five different automobiles. The primary purpose of the study was to compare sound quality evaluations made of interior vehicle noise during road tests with recordings of the noise of the vehicles played back to a jury of subjects using different playback methods. The experiment consisted of recording the sound fields inside the five cars with dual channel microphones situated in a dummy head. The study involved using a jury comprised of a large number of student subjects who first evaluated the sound quality of the five vehicles during the road tests, as well as later evaluating recordings of the same five vehicles played back through loudspeakers and headphones. It was found that there is a high correlation between the three different methods of evaluation used for the same vehicle. This study demonstrates that it is possible to evaluate the sound quality of a car in the laboratory with some confidence using the playback methods described in this paper. It also shows that laboratory evaluations, which are less expensive to conduct than road test evaluations, are good enough for manufacturers to determine the sound quality of a vehicle and to decide on the important sound quality factors needing improvement.
Engine Sound Comfortability: Relevant Sound Quality Parameters and Classification
In order to be able to shorten the design cycle, automobile manufacturers are interested in modelling the human perception of engine sounds. In the first part of the paper the relevant Sound Quality parameters for the prediction of engine sound comfortability are determined. The inputs are ordered with Automatic Relevance Determination and the obtained ranking is verified on the data. In the second part, models are presented to classify and compare cars on comfortability. Least Squares Support Vector Machines (LS-SVMs) is used for the classification. The influence of selecting the relevant inputs on the model performance is illustrated.
Combining subjective and objective assessments to improve acoustic comfort evaluation of motor cars
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A study leading to the establishment of the acoustic comfort index in motor cars is described. Five new light to medium hatch cars of different makes have been tested for two different conditions: public roads, and restricted test roads. Additional tests have also been carried inside an acoustic chamber using a roll dynamometer. Both subjective (jury) and objective with instrumental measurement have been carried out for the public road procedure, which involved three different road conditions, namely: high-speed highways, city centre roads and small gravel covered roads. Testing in the restricted circuit only involved objective measurements for two road conditions which were rough asphalt and smooth asphalt surfaces, where standard tests of speed and acceleration have been carried out. The universe of testers was composed of experienced drivers, all having some kind of experience in car engineering the remainder being NVH experts. They were asked to rank each car and provide a brief technical description of what they could hear during the test. The results were then compared with the measurements and treated using Statistics, in order to establish a series of comfort indexes, which have been developed and presented for each test condition. The idea was not only to establish a comfort index equation, but also mainly to provide alternatives to what is usually an expensive and time consuming procedure. It has been found that standard testing in closed test roads is able to characterise the comfort index, provided that the test conditions are well controlled. However further testing is still needed to improve these conditions so that the quality of results is compared with those obtained in the more usual way.
Applied Acoustics, 2013
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.
Wow, what car is that?: Perception of exterior vehicle sound quality
Noise Control Engineering Journal, 2003
Up until now most research and application in vehicle sound quality has been directed at describing interior vehicle sound quality. Even though the interior sound of a vehicle is a major component of the perceived sound quality, exterior sound is audible both to potential users and bystanders. It may be argued that interior vehicle sound quality is concerned with meeting the buyerʼs expectation, whereas exterior sound quality concerns a) attracting attention and positive responses of potential customers and b) minimizing negative responses in the general public. It may therefore be argued that optimizing exterior sound quality will benefit both consumers and the community. This article describes an approach to perceived exterior vehicle sound quality. To attain an understanding of exterior sound, we investigate both the semantic descriptions that are elicited when different exterior sounds are heard and specific situations (i.e. a given sound/vehicle in a given environment). Across different sounds and driving conditions we find four subjective dimensions: loudness/annoyance, perceived quality, low-frequency content, and temporal variations. This factor structure allows discriminating the sound quality of a variety of modern cars. In more specific tests we find that participants both discriminate between different vehicles and different environments (free field conditions, urban driving conditions as well as different street shapes). These results indicate that designing and predicting exterior sound quality is a multidimensional task that requires different approaches than those traditionally used for interior sound quality.
Sound quality evaluation of electric cars : preferences and influence of the test environment
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Many are the upcoming noise, vibration and harshness (NVH) challenges regarding electric vehicles (EV), not least due to absence of the masking combustion engine noise. In general, sound and vibration levels in the car's interior are significantly lower for EV's. However, tonal sounds caused by electromagnetic forces in the electric motor are in varying degrees present and provide audible feedback of operation during driving. The key question for how to target these sounds is to gain an understanding about what sound quality means for EV's. As an initial study, investigations were carried out to determine how the test environment influences the evaluation of the sound perception in an EV. Headphone evaluation with playback of binaural head recordings in both listening lab and a vehicle demonstrator "sound car" were compared to the real perception in a production-like electric car. A modified established scorecard for internal combustion engine (ICE) powertrain ...
Development of a Prediction Model of Acoustic Discomfort in Cars for Engine Idle Sounds
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Sound quality can be described as the relation between the perceptual reactions that reflect the customer's acceptance of a product that generates sound. Initially, A-weighted sound level was the only parameter used in the acoustic assessment. Since the 1950s, psychoacoustic investigations have contributed to enhance the correlation between hearing sensations and objective parameters that define the sound. Nowadays, the application of sound quality in product design is widely extended in the industry, being considered an important field study by the main automobile manufacturers. This aspect has become as important as other specifications that define the vehicle (design, equipment, colour, price...). Therefore, sound quality would be considered as a distinguishing factor that could contribute to the car purchase decision. This paper describes the development of a methodology to obtain a predicted model of acoustic annoyance applied to sounds of engines running on idle of compact cars, a feature that the customer can test in the car dealership in the process of purchase. Firstly, binaural recordings of eight car engines have been carried out by means of a digital artificial head placed on the seat of the driver. Main psychoacoustic parameters (level, loudness, sharpness, roughness...) were calculated. Afterwards, the design of a jury test was set up taking into account the kind of sounds to be evaluated. The recordings were presented to 12 subjects to assess the real sounds in a rate scale depending on the discomfort level perceived. The jury test was carried out in a laboratory where each subject listened to the recordings by means of headphones connected to an equalizer, making possible the reproduction of the sounds in an accurate binaural way and providing listeners with a realistic acoustic experience as if they were inside the vehicle. Finally, a model was established to predict the comfort rate for each sound using the psychoacoustic parameters as predictors.
Experience and information content affect interior vehicle sound quality assessments
International Journal of Vehicle Noise and Vibration, 2013
Recent research has found it useful to distinguish between the form and meaning of sounds. To investigate the relevance of meaning, naïve students and professional drivers listened to four levels of meaning neutralisation and four levels of spectral slope of recorded truck sound. Self-assessment of emotional reactions showed that professional drivers did not vary much in activation and rated over all lower activation than naïve participants whose affect ratings moved more or less along the annoyance correlation line in the upper left quadrant of the affect map. This gives some information about the importance of the source being recognisable and of previous user experience for product sound quality. It is further supported by that the overall difference between naïve participants' and professional drivers' ratings decreased with increasing meaning neutralisation. The methodology applied in the current study may be adopted to form homogenous panels of experts for sound evaluation.