Effects of Sound Absorption on Finite Amplitude Waveform Distortion

Abstract

Problems of nonlinear distortion for the acoustic wave of finite amplitude have been studied for a long time and some of the earlier works dealt with one-dimensional progressive waves in sound absorptionless media. This simplified model, however, does not always give an adequate representation in the majority of the cases of practical interest: analysis including spreading loss and sound absorption is necessary in some cases, for example, in the design of a horn loudspeaker. So this paper presents the theoretical predictions including these effects and experiments for farfield distortion in air. The approximate equation for the distortion coefficient of sound pressure in a free field, which is applicable for waves that do not contain shocks and not for nearfield distortion, is derived under some assumptions by using successive approximation. Then the experimental data on the main axis of a horn loudspeaker are given and compared with the theoretical values in Figs. 2, 3. The results show that the agreement between them is almost satisfactory and falls within the error limits of present work.