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- Hoffmann, Alice, 1983
(author)
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Perception of rolling noise
- 2015
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Licentiate thesis (other academic/artistic)abstract
- Due to improvements on combustion-engines and electric-engines for cars, tyre noisehas become the prominent noise source at low and medium speeds. Models existthat simulate the noise produced by a rolling tyre, as do models that auralize differenttraffic situations from a basic data set. When constructing a tyre it is of interestif improvements and planned changes are not only physically measurable, but thatthey also can be perceived. Focussing on that, two aims were followed in this thesis.The first aim was to combine an established model for tyre noise (SPERoN) withan auralization tool. The combined model can predict the spectrum of the soundat 7.5 m, as well as reproduce the sound for a given listener position. The auralizationuses a methodology where recorded sounds are converted to source signalsfor engine and tyre/road-interaction. These can be shaped by the spectra estimatedin SPERoN and synthesized back into a pass-by signal. Psychoacoustic judgementswere used to compare the modelled signals with recorded signals. To see how well themodelled signals match the real recorded signals for perception, two listening-testswere performed. The simulated and recorded signals were rated by pleasantness,loudness, roughness and sharpness using semantic differentials. It was found thatresponses for simulated and recorded signals correlate for all cases, but rankingscould not be reproduced exactly. The model can be further improved to be moreapplicable for listening tests. The model has been optimized after a first validation.The second aim laid focus on the perception of tyre/road noise. When designingtyre sounds, the main aim should be to increase the pleasantness of the total vehiclesound while maintaining the carried information and reducing the sound level. Tobe able to do this an understanding of how physical changes in a tyre are reflected inthe perception of the same tyre is essential. Thus, the second aim was to see if therolling noise of a tyre can be both differentiated and characterized by its perceptualqualities. The focus is on the perception of the sound outside the car, perceived byfor example a pedestrian. Listeners have judged different road tyre combinationsand their perception in terms of their emotional responses (pleasantness, activationand stress) and their psychoacoustic responses (loudness, sharpness, roughness, andpitch). The results confirmed that rolling noise can be perceptually differentiated. Itis further possible to differentiate between the effects of the street and the effects ofthe tyre on all emotional and most psychoacoustic parameters. The results suggestthat changes to road surfaces or tyres can affect both emotional and psychoacousticperceptual qualities.
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| 2. |
- Hoffmann, Alice, 1983, et al.
(author)
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There’s a car coming? - Psychometric function for car pass-by in background noise based on simulated data
- 2015
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In: Euronoise 2015, 10th European Congress on Noise Control Engineering. - 2226-5147. ; , s. 2417-2421
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Conference paper (peer-reviewed)abstract
- To detect an approaching car in background noise is an important aspect of traffic safety. Therefore itis essential to understand the determinants that makes people recognize an approaching car especiallywhen the cars become very quiet at low speeds as it is the case for electrical cars for instance. Moststudies on the detection of passenger cars in background noise are based on recorded signals. Thisrequires that suitable recordings are available both for the background sound as well as the test sound(i.e. the sound of the approaching vehicle). Due to the limited control of such situations the degreesof freedom to be varied in such experiments is limited as well. In the presented study a differentapproach has been employed. The utilized sounds are based on an auralization method that allowsfor simulating vehicle sounds including both tyre/road noise and propulsion noise. Single car eventscan thus be superposed to background sound with full control of all relevant parameters. The usedauralization method has in earlier studies been validated for giving good perceptual ratings comparedto recorded sounds. The method allows for evaluating the psychometric functions for single parametersand hopefully give a deeper understanding of the perceptual space for a car in background noise. Inthe present study the reaction time is measured for the detection of a car (test vehicle) passing byin the presence of background noise from a road with high traffic flow. The distance between the thepath of the test vehicle and the highly trafficked road is varied. All other parameters (i.e. car-type,road surface, speed, etc.) are kept constant. The study shows that there is a logarithmic relationbetween the response times and the distance between the the track of the test car and the road withhigh traffic volume. At the same time there is a linear relation between reaction time and signal tonoise ratio (i.e. the equivalent sound pressure level in relation to the background level).
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