Sound localization in headphone reproduction by simulating transfer functions from the sound source to the external ear

Experiments simulating sound fields radiated from a loudspeaker by using headphones are described. Comparing the differences in characteristics between the sound reproduced through a loudspeaker and that through headphone, speaker listening conditions were simulated by a headphone listening using digital signal processing techniques on the following two aspects: the static state transfer function from the loudspeaker to the external-ear entrance of a subject (referred to as “head-related transfer function” here); and the dynamic change in interaural time difference (ITD) caused by head movement of the subject. When only the static transfer function was simulated, perceived sounds were mostly localized at the intended direction outside subject's head, but a front-rear confusion was often observed when the intended direction was near the median plane. Furthermore, perceived distances of sounds are generally shorter than intended ones. When the dynamic changes in interaural time difference are simulated in addition to the static head-related transfer functions, however, the front-rear confusion remarkably decreased and natural sound localization was achieved.