Single transducer parametric sound source

Abstract

The idea of using the nonlinear effects of the propagation of sound waves with finite amplitude to build up highly directed sound sources is well known. In underwater acoustics, such parametric arrays are widely used. There are also attempts to build up parametric arrays in air to generate highly directed air-borne sound. To be able to use nonlinear effects in air as a carrier medium, one needs high amplitudes of the propagating sound wave. Consequently, a superposition of single sound sources (arrays) is often reported in the literature to increase the size, and so the directivity, of the sound source as well as the acheived sound pressure level. A major disadvantage of using arrays is the problem of slightly varying resonance frequencies and phase characteristics of the single source components as well as a complicated superposition of single directivity patterns. It is difficult to investigate basic properties of wave propagation and the nature of distortion in such a way. In this work, a single, high-power ultrasound transducer was used to radiate sound waves with finite amplitude, able to generate extraneous frequency components in air. Using only a single transducer, it was possible to investigate basic properties of nonlinear wave propagation in air.