There’s a car coming? - Psychometric function for car pass-by in background noise based on simulated data

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)