Abstract
Time reversal is a method often used to focus sound to a desired location, and works best in a reverberant environment. The effect of focus location within a reverberant environment is presented first, revealing that proximity to reflecting surfaces has a significant effect on the amplitude of the focus both experimentally and when using a modal summation model. These effects are a primary component to creating focus signals at high amplitudes. High-amplitude focusing experiments show that when multiple sources are used simultaneously to generate a focus, a peak amplitude pressure spike of 200 dB can be achieved in air. A pressure spike of this amplitude has multiple nonlinear characteristics, and an investigation into the spatiotemporal features and harmonic content of these signals was conducted. The peak amplitude of the focus signal also increases in amplitude nonlinearly as the loudspeaker volume is linearly increased. This nonlinear increase is the primary subject of investigation in this work. Experimental and computational methods are implemented in order to understand the mechanisms driving the nonlinear increases observed when the sources are combined acoustically as opposed to linear superposition of the contributions from each sound in post-processing. Finally, models of converging high-amplitude waves are generated using the k-Wave© package for MATLAB©. These show a similar nonlinear increase in amplitudes, supporting the hypothesis of a Mach wave coalescence. A COMSOL© finite element model allows visualization of the converging waves with Mach stems forming in free space to cause the nonlinear amplification.
Degree
PhD
College and Department
Physical and Mathematical Sciences; Physics and Astronomy
Rights
https://lib.byu.edu/about/copyright/
BYU ScholarsArchive Citation
Patchett, Brian D., "Focusing of High-Amplitude Sound Waves Using the Time Reversal Process" (2022). Theses and Dissertations. 10196.
https://scholarsarchive.byu.edu/etd/10196
Date Submitted
2022-12-08
Document Type
Dissertation
Handle
http://hdl.lib.byu.edu/1877/etd13034
Keywords
acoustics, nonlinear, time reversal, high amplitude, focus, focus sound, loud, acoustic signal processing
Language
english