Nonlinear Distortion Characteristic Analysis for the Finite Amplitude Sound Pressures in the Pistonphone

Abstract

The wide concern on absolute calibration of microphones at high pressure levels prompts the development of the pistonphone technique. However, as the sound pressure level goes higher, the linear hypothesis, which is applicable for the small amplitude sound wave, will no longer be valid. The nonlinear characteristics of the finite amplitude sound wave will produce high order harmonic components and also some other complex frequency components, which eventually result in the distortion of the sound pressure in the pistonphone, and should be quantitatively calculated to assess the accuracy of absolute sound pressure calibration of microphones at high sound pressure levels using pistonphones. In this paper, the linearized wave equations were built based on the perturbation method and the Euler system. Then, the distributed parameter expressions for the finite amplitude sound pressure both neglecting and considering the intermodulation characteristic have been explicitly derived. Nonlinear distortion characteristics of the sound pressure in the pistonphone have been studied, and the effects of the intermodulation on the sound pressure distortion have been evaluated. Computations reveal that the nonlinear distortion characteristics of the sound pressure produced by pistonphones should be quantitatively considered when the sound pressure level reaches 148[Formula: see text]dB, and the intermodulation characteristic can be neglected when the sound pressure level is lower than 174[Formula: see text]dB.