Problems in nonlinear acoustics: Scattering of sound by sound, parametric arrays, focused sound beams, and noncollinear tone-noise interactions

Abstract : Five projects are discussed involving nonlinear acoustics. (1) Scattering of Sound by Sound, a theoretical study of two noncollinear Gaussian beams which interact to produce sum and difference frequency sound. (2) Parametric Receiving Arrays, a theoretical and numerical study of parametric reception in a reverberant environment. (3) Noncollinear Interaction of a Tone with Noise, an experimental investigation of the nonlinear interaction which occurs when the two waves propagate in different modes of a rectangular duct. (4) Nonlinear Effects in Focused Sound Beams, a preliminary analytical study of harmonic generation in the focal region. (5) Parametric Ultrasonic Proximity Sensor, a numerical investigation into the use of a parametric array as an ultrasonic proximity sensor in air. Keywords: Nonlinear acoustics; Parametric array; Acoustic arrays; Scattering of sound by sound; Focused sound; Waveguide; Noise.