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UNDERWATER SHOCK WAVE FREQUENCY SPECTRUM ANALYSIS. I. SIMPLE WAVEFORMS APPROXIMATING MEASURED PRESSURE PULSES IN WATER
NAVAL ORDNANCE LAB WHITE OAK MD
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A Fourier integral analysis is presented for simple waveforms approximating the more common underwater shockwave pulses the waveforms treated are the exponential, exponential modified by the recorder frequency characteristics, exponential modified by reflection and cutoff, triangular, and square. A cosine pulse, such as is emitted by sonar transducers, is also shown for comparison. Analytical expressions for the amplitude spectra are summarized and the frequency composition is shown graphically in non-dimensional form for most of the functions. Some of the experimental conditions and recorder characteristics which may produce the various waveforms are noted. The effect upon the frequency composition of the superposition of identical pulses displaced by equal time increments is also discussed. These spectrum analyses, although approximate, permit a better understanding of the relationship between the frequency spectra and the waveforms of underwater shockwaves. Author
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