A summary of the sound pressure level transformations from free and diffuse sound fields to the human torso, head, and ear

Abstract

The sound pressure level (Lp) measured at a particular location on the human head or torso differs from the level in the empty sound field because sound is scattered by the head and body. The difference between the level measured near the head or torso and the level measured in the empty field is defined here as the sound pressure level transformation. Previous measurements of these transformations are summarized and presented as a function of frequency, microphone location, type of incident sound field, and angle of incidence (in the horizontal plane). For the most part, these transformations are positive: the levels near the head or torso are greater than those in the empty sound field. Differences in the results of various studies are pointed out. Further studies are proposed to resolve the differences and provide additional information. Some simple guidelines for choosing a free or diffuse field transformation in a real environment are presented. The choice depends on source directivity, distance betw...