An investigation of the combustive sound source
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This thesis describes the development and testing of the Combustive Sound Source (CSS), which is a broadband underwater sound source. The CSS is being developed as a clean, safe, and cost effective replacement to underwater explosive charges, which exhibit an inherent danger to marine life and researchers using the charges. The basic operation of the CSS is as follows. A combustible mixture of gas is held below the surface of the water in a combustion chamber and ignited with an electric spark. A combustion wave propagates through the mixture and converts the fuel and oxidizer into a bubble of combustion products, which expands due to an increase in temperature, and then ultimately collapses to a smaller volume than before ignition, producing a high intensity, low frequency acoustic signal. The thesis begins by discussing the background, history, and purpose of developing the CSS. It continues by describing the current apparatus and the essential components and convenient features added to the latest mechanical design. The general operation is discussed along with a description of an experiment conducted to determine the acoustic output and robustness of the current CSS. The results of this experiment are presented in terms of the effect of volume, ignition depth, oxidizing gas, combustion chamber size, and repeatability of acoustic signatures. Discussion of apparatus robustness is presented to suggest improvements for future CSS designs.