Determination of monaural sensitivity changes due to the pinna by use of minimum-audible-field measurements in the lateral vertical plane

Abstract

Monaural minimum-audible-field (MAF) measurements were taken for 5 [human] subjects at 7 angles of source elevation, .PHI.(-60.degree. .ltoreq. .PHI. .ltoreq. + 60.degree.), in the lateral vertical plane containing the interaural axis. These measurements were made by automated method of limits threshold determinations, using narrow-band random noise (center frequencies 4-16 kHz), emitted from a special point source. A method was devised for extracting from the MAF data, functions which display the elevation-dependent changes in sensitivity, primarily caused by the pinna. Most of these derived functions contained a narrow response dip, whose minimum increased in frequency from .apprx. 6.5 kHz monotonically to .apprx. 14 kHz, with increasing source elevation. For corresponding elevations there were many intersubject similarities in these derived response functions and also strong agreement with known data regarding the pinna''s acoustic response. The percept of source elevation may be based upon the detection of the relative absence of specific high-frequency spectral- energy content related to minima in the pinna''s response functions.