Head-Related Transfer Function

The Head - Related Transfer Function ( HRTF usually only briefly, rare head -related transfer function or outer ear transfer function ) describes the complex filtering effects of head, outer ear ( pinna) and trunk. This amplitude evaluation is in addition to the travel time differences between the ears fundamental to our acoustic localization system.

The elevation of the sound source does not cause run-time differences, nor would such a distinction between frontal and rear sound source over the otherwise fundamental for our localization time difference possible. In the overtone runtime localization fails completely because several wavelengths of the sound fit in the ear distance and the evaluation thereby ambivalent.

Therefore, we are also dependent on the evaluation of amplitude differences. This increase with frequency because diffraction effects at the head and trunk are stronger at shorter wavelengths. With further increasing frequencies allow angle-dependent resonance phenomena on the outer ear, the localization in the elevation plane.

In principle, these increases and decreases in the Blue Chen bands are described, but especially the location of the zeros in the resonance phenomena individually very different. Because the HRTF localization is mainly based on learned stimulus patterns, no generalized function can be specified due to the anatomical differences. The dummy head stereophonic, based on this filter effect, works satisfactorily only if the differences from the hearing person are not too large.

Wherein based phantom source speaker reproducing the complex filtering action of the outer ear results in significant errors, because the angle of incidence of the wave fronts often does not correspond to the original sound field. Thus, large amplitude errors are caused, among other things lead to the known elevation of the phantom center (center) at the loudspeaker stereophony. Remedy could bring only a physical reconstruction of the original sound field, as it is aimed at holophony approach.