Spatial perception, the acoustics of the external ear, and interactions with earphones

Abstract

In free-field listening, the perception of source elevation and discrimination between forward and rearward source positions appear to be largely dependent on the availability of high-frequency spectral cues associated with the mode structure of the concha and diffraction by the pinna, respectively. The role of the concha is particularly clear between 5 and 10 kHz, while pinna-diffraction effects are strongly developed between 2.5 and 6 kHz. When sounds are presented through earphones, the free-field characteristics of the ear are replaced by very different characteristics that are dependent on complex and unreliable interactions between the individual earphone and the individual ear. Since these interactions are highly dependent on earphone design, it may be appropriate to focus attention on the special characteristics that may be desirable in earphones intended for use in the creation of virtual acoustical environments. These may include coupling that (i) allows the response at the eardrum to follow the primary resonance curve of the individual ear and (ii) minimizes the inter- and intrasubject variations in response to other frequencies, including frequencies above 5 kHz where the wave characteristics of the concha come into play.