Embedding Distance Information in Binaural Renderings of Far Field Recordings

Traditional representations of sound fields based on spherical harmonics expansions do not include the sound source distance information. As multipole expansions can accurately encode the distance of a sound source, they can be used for accurate sound field reproduction. The binaural reproduction of multipole encodings, though, requires head-related transfer functions (HRTFs) with distance information. However, the inclusion of distance information on available data sets of HRTFs, using acoustic propagators, requires demanding regularization techniques. We alternatively propose a method to embed distance information in the spherical harmonics encodings of compact microphone array recordings. We call this method the Distance Editing Binaural Ambisonics (DEBA). DEBA is applied to the synthesis of binaural signals of arbitrary distances using only far-field HRTFs. We evaluated DEBA by synthesizing HRTFs for nearby sources from various samplings of far-field ones. Comparisons with numerically calculated HRTFs yielded mean spectral distortion values below 6 dB, and mean normalized spherical correlation values above 0.97