Many articles and text books have treated acoustic filters from various viewpoints, and acoustic filter experiments have been devised for laboratory courses in acoustics. These experiments frequently point out the analogy between lumped-constant acoustic filters and electrical filters, in order to make use of the many texts and handbooks dealing with electrical filter theory and construction. Although it is clear that electrical filters are designed to operate from a specified source impedance and into a specified load impedance, the laboratory experiments which the author has seen do not apply this requirement to the acoustic filters used. The present article describes an acoustic source with a primarily resistive output impedance, a microphoen assembly which serves as a primarily resistive load impedance and detector, and a low-pass acoustic filter designed to match them. The analogous electrical filter was built, and the performance characteristics of the two filters are compared.
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Seismic Wave Propagation: Collected Works of J. E. White
This first chapter sets the stage for the later technical development of Dr. Whit’s career in applied seismics. Experiments, f’wst at the Acoustics Laboratory of the Massachusetts Institute of Technology and later at Mobil Oil and Marathon Oil, provided insight into the general problems of impedance measurements, transduction, filtering, and attenuation. These papers also serve as a bridge to show geophysicists how theft own experiments in seismology naturally interface with (indeed, arose out of) the larger world of sound measurements in air and water. These experiments demonstrate the power of geometrically constrained experiments to allow verification of approximate (and in some cases, exact) theories of sound.