A Formula for Low-Frequency Interaural Level Difference

It is well-known that low-frequency (i.e., less than about 700 Hz) interaural level difference (LF-ILD) is an important cue for near-field distance perception, and is particularly important in environments with limited reverberation. For applications (e.g., virtual and augmented reality consisting of moving sound sources) where spatial audio needs to be synthesized in real-time and reproduced over headphones or a pair of crosstalk-cancelled loudspeakers, a simple and efficient method for incorporating a source distance and direction-dependent LF-ILD is required. In this talk, a formula is presented for computing LF-ILD as a function of source distance and direction. The main steps involved in analytically deriving the formula from rigid-sphere head-related transfer function theory are shown. Using an example, it is shown that the formula may be used to compute the LF-ILD as a function of sound source location accurately for a given individual and exactly for a rigid sphere.