Spatial acoustic measurement in rabbits and humans and neural spatial tuning in the midbrain of the rabbit.

Abstract

There are only a handfull of studies that address the effects of sound source distance on the head‐related transfer function (HRTF). We found in rabbits and humans that (1) the spectral shape of the HRTF changed with sound source location; (2) ILD increased with decreasing distance and increasing frequency. ILDs can be substantial even at low frequencies when distance is close; and (3) ITD decreased with decreasing distance and generally increased with decreasing frequency. These findings refute the common notions that ILD is negligible at low frequencies and that ITD is constant across frequency. Neural coding of using virtual auditory space (VAS) stimuli was investigated in the inferior colliculus of the unanesthesized rabbit. The bulk of our neurons were tuned to azimuths on the contralateral side (re: recording site) with best azimuths ranging from 0 to 90 deg. This tuning tended to broaden with stimulus level, although the degree of level tolerance differed among neurons. At low sound levels, the azi...