Problems in Nonlinear Acoustics: Parametric Receiving Arrays, Focused Finite Amplitude Sound, & Noncollinear Tone-Noise Interactions

Abstract : Three projects are discussed in this report. (1) Parametric Receiving Arrays. This project is a theoretical investigation into the use of a parametric receiving array for directive measurements of noise radiated by ships in reverberant environments. The analysis is based on a Gaussian beam model that takes nearfield diffraction into account. The scattering of sound is also investigated. (2) Focused Finite Amplitude Sound. A numerical solution is used to investigate the combined effects of nonlinearity, diffraction, and absorption on sound that propagates through a focal region. The analysis yields time waveforms, axial propagation curves, spectral power distributions, and beams patterns. (3) Noncollinear Tone-Noise Interactions. The noncollinear interaction of a pure tone and a band of noise that propagate in different modes of a rectangular duct is investigated both experimentally and theoretically. Keywords: Nonlinear acoustics; Parametric array; Scattering of sound by sound; Focused sound; Waveguide; Noise.