Investigation of an auditory thresholds for early reflections in car-cabins

A current challenge that NVH engineers are asked to face is to optimize the passengers' acoustic experience in vehicle cabins. The combined use of sound source localization techniques and auralization tools can help in tackling such issue. Data from the source localization step, i.e. sources and early reflections, can be auralized in order to assess the acoustic quality of the cabin. However, the remaining question is to understand how many reflections are effectively needed for providing a realistic listening experience. By varying the order of early reflections included in the auralization step, a different Auditory Spatial Impression (ASI) is perceived by humans. At a certain point, increasing the reflections order does not change the ASI and the rest of reverberations can be replaced by a constant reverberation tail. This paper aims at defining the optimal reflections order that is necessary to use for in-vehicle sound auralization purposes. A ray tracing model of a car cabin is used for generating the data set containing the sound samples auralized by changing the number of reflection orders. Results from subjective tests are presented to show the correlation between ASI in the cabin and the optimal number of reflection orders used in the auralization.