Measurement of Sound Absorption Coefficients with Acoustic Pulses

Abstract

Sound absorption coefficients of acoustical materials are commonly measured by the reverberation chamber technique, thereby requiring knowledge of the characteristics of the chamber. Use of acoustic pulses allows determination of reflection coefficients and absorption coefficients without the use of a special chamber, since the pulse reflected from the sample of material may be isolated from other pulses arising from reflections from other surfaces if the pulses be short enough. An essentially plane wave front is obtained by use of a parabolic reflector behind the source of pulses. To compare results from the pulse measurements with data from reverberation chamber measurements, variation of angle of incidence must be carried out in the pulse measurements, and frequency must be varied in the chamber measurements. A preliminary measurement at one-pulse frequency shows satisfactory agreement between the two methods.