Auditory localization of a nearby point source

Although human auditory localization has been studied extensively in the past century, little is known about the localization of nearby sound sources. The head‐related transfer function (HRTF) contains all relevant localization information and has been thoroughly examined for relatively distant sources, but may exhibit unique properties in the ‘‘near‐field’’ region within 1 m of the center of the head. A rigid‐sphere computational model of the head has been used to estimate near‐field HRTFs, and a KEMAR manikin and a specialized acoustic ‘‘point’’ source have been used to measure HRTFs for sources as close as 0.25 m. For a fixed source direction, the interaural time delay is roughly independent of distance, but the interaural amplitude difference increases dramatically as the source approaches within 1 m of the head. When the source is near one ear, the interaural amplitude difference exceeds 20 dB across the audio spectrum. The differences between near‐field and more distal HRTFs will be discussed, inclu...