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Colloquium, Spring 2005

Day: Tuesday May 24th Time: 4:00pm Place: BH 112 Title: Measuring Underwater Acoustic Signal with the Fourier Transform Speaker: Joel Hibbard, WWU As submarines grow increasingly quiet, ambient ocean noise drowns out their sound and they become undetectable to a microphone or a simple system of microphones. This is sometimes an advantage, but it makes detection and measurement of friendly submarines impossible with existing facilities. Historically, navies have employed various techniques to direct their underwater listening, but transforming sound with the Fourier transform provides the best tools to reduce undesirable noise in a detection system. Applying this theory to acoustics requires an appropriate domain of definition for the transform, an understanding of the delta distribution, and a definition for the Fourier transform of distributions. With these foundations laid, scientists can characterize the response of an array of hydrophones, manipulate its sensitivity to exclude noise, and increase sensitivity to particular signals by weighting the input from individual phones with complex constants. What is all this useful for? Why such emphasis on precise submarine acoustic measurements? The Navy has a specific tactical goal behind this area of research, which requires application of linear algebra and will be discussed at the end of the talk. Optimal array design and signal processing apply not only to acoustic fields, but are expected to advance the processing of electromagnetic waves for radar and visual detection. Cookies: In BH 300 at 3:30pm.