Acoustical nonlinearities in compression chambers and horns of horn drivers

Abstract

A horn driver is an essential part of sound reinforcement systems. Principles of horn driver operation are associated with generation of acoustical nonlinear distortion. Distortion is generated in a compression chamber by nonlinear compression, and by modulation of air stiffness, mass, and viscous losses, and a nonlinear relationship between particle velocity and sound pressure. Distortion is also generated in the phasing plug and horn by propagation of high amplitude waves. The effect of compression chamber air mass and viscous losses modulation and nonlinearity has not been researched previously. The analysis of modulation and nonlinear effects in the compression chamber is based on analysis of variation of the compression chamber’s air moving mass, viscous losses, and compliance as a function of the diaphragm’s instantaneous position and level of acoustical pressure. The pressure and diaphragm position-dependent parameters are incorporated into the system of nonlinear differential equations governing movement of the diaphragm and oscillation of air in compression chamber. Analysis of nonlinear propagation effects in the phasing plug and horn is based on numerical solution of an implicit nonlinear equation for propagation of finite amplitude sound waves. The work results in the methodology of simulation dynamic performance of horn drivers and provides comparative analysis of different acoustical nonlinear and parametric mechanisms.