Efficient construction of the spatial room impulse response

An important component of the modeling of sound propagation for virtual reality (VR) is the spatialization of the room impulse response (RIR) for directional listeners. This involves convolution of the listener's head-related transfer function (HRTF) with the RIR to generate a spatial room impulse response (SRIR) which can be used to auralize the sound entering the listener's ear canals. Previous approaches tend to evaluate the HRTF for each sound propagation path, though this is too slow for interactive VR latency requirements. We present a new technique for computation of the SRIR that performs the convolution with the HRTF in the spherical harmonic (SH) domain for RIR partitions of a fixed length. The main contribution is a novel perceptually-driven metric that adaptively determines the lowest SH order required for each partition to result in no perceptible error in the SRIR. By using lower SH order for some partitions, our technique saves a significant amount of computation and is almost an order of magnitude faster than the previous approach. We compared the subjective impact of this new method to the previous one and observe a strong scene-dependent preference for our technique. As a result, our method is the first that can compute high-quality spatial sound for the entire impulse response fast enough to meet the audio latency requirements of interactive virtual reality applications.