Microphone placement factors for one-half inch diameter microphones

Abstract

A series of tests were conducted to compare the measurement of an undisturbed acoustical field with a 1/2-in.-diam microphone to the measurement of the aocustical sound with a 1/2-in.-diam, shoulder mounted, man-worn microphone. One-third octave band spectrum measurements were made and the positional-center head microphone placement factor was determined for three shoulder positions, and five microphone orientations. The acoustical tests were performed in a reverberation room and in an anechoic chamber on five test subjects. The free field measurements were conducted for azimuthal angles from 0°–360° in increments of 45°. Averaged microphone placement factors are presented for a 1/2-in.-diam microphone, in one-third octave bands, from 200 to 8000 Hz, for all test locations, microphone orientations, and acoustical environments. Where possible comparisons are made between the results of this study and, earlier work which determined the microphone placement factors for a 1-in.-diam microphone. A computation of the best microphone location orientation was made for four defined types of noise spectra. This was done in order to predict the optimum position for the location of a noise dosimeter microphone under free and diffuse field conditions.