AURALIZATION, PERCEPTION AND DETECTION OF TYRE–ROAD NOISE
Doctoral thesis, 2016
Due to improvements in combustion engines and electric engines for cars, tyre noise has become the prominent noise source at low and medium speeds. Models exist that simulate the noise produced by a rolling tyre, as do models that auralize specific traffic situations from a basic data set. A model that combines both could assist in the planning stage of a tyre by delivering not only estimates of the physical behaviour of the tyre, but also by further making the resulting sound perceivable. Further, such a model could help to design acoustic traffic situations with full control of all parameters. Focusing on that, this thesis has three aims. All focus is on the perception of the sound of a car from the outside, perceived by, for example, a pedestrian. The first aim is to combine an established model for tyre noise (SPERoN) with an auralization tool. The combined model can predict the spectrum of a car pass-by at 7.5 m, as well as reproduce the sound at a given listener position. Psychoacoustic judgements are used to compare the modelled signals with recorded signals. It was found that responses for simulated and recorded signals correlated for all cases, but the ranked orders differed slightly. The second aim focuses on the perception of tyre–road noise and whether it can be differentiated and characterized by its perceptual qualities. When designing tyre sounds, the main aim should be to increase the pleasantness of the total vehicle sound while maintaining the carried information and reducing the sound level. Achieving this requires an understanding of how physical changes in a tyre are reflected in the perception of that tyre. Listeners were asked to judge different tyre–road combinations and their perception in terms of their emotional and psychoacoustic responses. The results confirmed that rolling noise can be perceptually differentiated. The third aim in this thesis was to increase understanding of the parameters that influence the detection of a single car in background traffic noise. For this, both variations in the sound of the test car and in the background (e.g. distance, traffic amount, speed, tyre/engine noise) were investigated and found to influence the reaction time. The introduced auralization method was utilized to generate the sound files for the different traffic situations.
Perception
Psychoacoustics
Rolling Noise
Traffic Detection
Reaction Time
Auralization
Tyre/Road Noise
EA-salen, Hörsalsvägen 11
Opponent: Prof. Dr.-Ing. habil. Ercan Altinsoy, Institute of Acoustics and Speech Communications, Technical University Dresden, Germany.
Author
Alice Hoffmann
Chalmers, Civil and Environmental Engineering, Applied Acoustics
Optimierung der Auralisierung von Reifengeraeuschen basierend auf dem Modellierungs-Tool SPERoN
Akustik und Audiologie - "Hören für alle"; DAGA 2014, 40. Jahrestagung für Akustik "Fortschritte der Akustik", 10. - 13. März 2014, Oldenburg, Germany,;Vol. 40(2014)p. 178-179
Paper in proceeding
Auralization of tyre/road noise based on the SPERoN prediction tool
Proceedings of AIA-DAGA 2013 Conference on Acoustics, Meran, Italy, March 18-21, 2013,;(2013)p. 114-117
Paper in proceeding
There’s a car coming? - Psychometric function for car pass-by in background noise based on simulated data
Euronoise 2015, 10th European Congress on Noise Control Engineering,;(2015)p. 2417-2421
Paper in proceeding
A. Hoffmann, P. Bergman, W. Kropp, Perception of tyre noise: Can tyre noise be differentiated and characterized by the perception of a listener outside the car?
A. Hoffmann, W. Kropp, Psychometric function for car pass-by in background noise based on simulated data
J. Forssén, A. Hoffmann, W. Kropp, Auralisation model for the perceptual evaluation of tyre-road noise
A. Hoffmann, W. Kropp, Auralization of simulated tyre noise: psychoacoustic validation of a combined model.
Standing at the side of a road, one can hear the sound of the cars passing by. In cities, where the speed of the cars barely exceeds 50 km/h, the main noise from the car consists of the tyres, rolling on the road surface. For environmentally conscious cities, it is of interest to reduce that tyre noise. To assist tyre manufacturers in their development of new products, this thesis introduces a tool that creates an acoustic impression on how a newly designed tyre or road surface might sound. For this, no expensive manufacturing of test samples is needed. The sounds can simply be generated based on the design properties of tyre and road.
In one of the investigations, a group of sound examples was generated and used to find out how it is possible to differ between sounds generated by different tyres or road surfaces. The sound can for instance differ in how loud it is, how rough it sounds and how pleasant it sounds. It was investigated which descriptors that can be used to describe and differ between different tyres and road surfaces.
Another aspect that was investigated in this thesis is how different tyres and road surfaces assist us in detecting, or not noticing an approaching car in traffic. Normally, recordings of traffic noise are used for such investigations. The tool presented in this study allows to do these types of investigations much faster and cheaper. Even newly designed tyres and road surfaces can be used. In listening experiments, the reaction time until a pedestrian noticed an approaching car in background traffic noise was measured. With this method, different traffic situations were tested. It was found that distance between test car and background traffic, traffic amount of the background traffic and the speed of both test car and background could strongly affect the reaction time. Further, electric cars were tested against combustion cars. The increase in reaction time for the electric cars was smaller than expected. Additional warning sounds in form of added single tones were able to improve the detection. But this only helped, if they were not present in the background as well. An interesting finding was, that a decrease of 6 dB in the level of the background traffic noise, clearly improved earlier detection. If the background levels were below 50 to 55 dB, test cars were detected sufficiently early in all cases.
In one of the investigations, a group of sound examples was generated and used to find out how it is possible to differ between sounds generated by different tyres or road surfaces. The sound can for instance differ in how loud it is, how rough it sounds and how pleasant it sounds. It was investigated which descriptors that can be used to describe and differ between different tyres and road surfaces.
Another aspect that was investigated in this thesis is how different tyres and road surfaces assist us in detecting, or not noticing an approaching car in traffic. Normally, recordings of traffic noise are used for such investigations. The tool presented in this study allows to do these types of investigations much faster and cheaper. Even newly designed tyres and road surfaces can be used. In listening experiments, the reaction time until a pedestrian noticed an approaching car in background traffic noise was measured. With this method, different traffic situations were tested. It was found that distance between test car and background traffic, traffic amount of the background traffic and the speed of both test car and background could strongly affect the reaction time. Further, electric cars were tested against combustion cars. The increase in reaction time for the electric cars was smaller than expected. Additional warning sounds in form of added single tones were able to improve the detection. But this only helped, if they were not present in the background as well. An interesting finding was, that a decrease of 6 dB in the level of the background traffic noise, clearly improved earlier detection. If the background levels were below 50 to 55 dB, test cars were detected sufficiently early in all cases.
Areas of Advance
Transport
Subject Categories
Transport Systems and Logistics
Vehicle Engineering
Fluid Mechanics and Acoustics
Signal Processing
ISBN
978-91-7597-469-9
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4150
Publisher
Chalmers
EA-salen, Hörsalsvägen 11
Opponent: Prof. Dr.-Ing. habil. Ercan Altinsoy, Institute of Acoustics and Speech Communications, Technical University Dresden, Germany.