A binaural model to evaluate surround sound reproduction systems using head movements.

Abstract

Recently, a binaural model was proposed, which utilized head movements to resolve front-back confusions [Braasch et al., J. Acoust. Soc. Am. 127, 1886]. Meanwhile, the binaural model has been extended to evaluate the benefit of surround loudspeakers for the reproduction of diffuse sound. For this purpose, two to four loudspeaker locations were simulated using head-related transfer functions (HRTFs). To simulate head movements, the HRTFs were adjusted in steps of 1 deg to maintain the loudspeaker positions in a room-related coordinate system. Uncorrelated white-noise bursts (1-s duration) were fed to each loudspeaker channel. The superposed spatialized signals were processed through a gammatone filter bank to measure coherence and interaural-level (ILDs) differences in individual frequency bands. Various loudspeaker configurations were tested. The study shows that coherence and ILDs for diffuse sound vary less with head movements if surround speakers (e.g., ±120 deg) are used in addition to a pair of front speakers (e.g., ±30 deg). For example, if the head is turned between ±40 deg, the maximum coherence drops from 0.58 to 0.39 if surround loudspeakers are added (600-Hz frequency band). At 5000 Hz, the maximum ILD magnitude is reduced from 10 to 4 dB with surround loudspeakers.