Virtual Reality for Subjective Assessment of Sound Quality in Cars

Binaural recording and playback has been used for decades in automotive industry for performing subjective assessment of sound quality in cars, avoiding expensive and difficult tests on the road. Despite the success of this technology, several drawbacks are inherent in this approach. The playback on headphones does not benefit of head-tracking, so the localization is poor. The HRTFs embedded in the binaural rendering are those of the dummy head employed for recording the sound inside the car, and finally there is no visual feedback, so the listener gets a mismatch between visual and aural stimulations. The new Virtual Reality approach solves all these problems. The research focuses on obtaining a 360° panoramic video of the interior of vehicle, accompanied by audio processed in High Order Ambisonics format, ready for being rendered on a stereoscopic VR visor. It is also possible to superimpose onto the video a real-time colormap of noise levels, with iso-level curves and calibrated SPL values. Finally, both sound level colormap and spatial audio can be filtered by the coherence with one or multiple reference signals, making possible to listen and localize very precisely noise sources and excluding all the others. These results have been acquired employing a massive spherical microphone array, a 360° panoramic video recording system and accelerometers or microphones for the reference signals.