A New Inverse Processing Approach to the Modeling of Head-related Transfer Functions for Audio Spatialization

Currently, achieving high-fidelity sound spatialization requires the prospective user to undergo lengthy measurements in an anechoic chamber using highly specialized equipment. This, in turn, has increased the cost and reduced the availability of high-fidelity spatialization to the general public. An attempt to generalize 3D audio has been made using the measurement of a KEMAR dummy head or creating a database containing a sample of the public. Unfortunately, this leads to increased front/back reversals and localization errors in the median plane. Customizable Head-Related Impulse Responses (HRIRs) would reduce the errors caused by general HRIRs and remove the limitation of the measured HRIRs. This paper reports an initial stage in the development of customizable HRIRs. The ultimate goal is to develop a compact functional model that is equivalent to empirically measured HRIRs but requires a smaller number of parameters that could be obtained from the anatomical characteris tics of the intended listener. In order to arrive at such model, the HRIRs must be decomposed into multiple scaled and delayed damped sinusoids, which would reveal the parameters that the compact model needs to have an impulse response similar to the measured HRIR. Previously this type of HRIR decomposition has been accomplished through an exhaustive search of the model parameters. A new method that approaches the decomposition simultaneously in the frequency (Z) and time domains is reported here. INTRODUCTION Virtual spatial audio has been applied in many areas from computer video games to assistive technology for the visually impaired. Spatial audio is the ability that allows humans to locate a sound source in three-dimensional (3D) space (Fig. 1). Fig. 1: Diagram of a sound source in 3D space There are currently two methods for creating virtual spatial audio: the multi-channel and the two-channel approach. The multi-channel approach consists of physically positioning speakers around the listener (e.g., Dolby 5.1 array). This method is effective but requires expensive equipment and relies in the relative positions of the listener and the speakers, which limits its portability. AZIMUTH DISTANCE Sound