An article by R. D. Fay presents a method for calculating the complete performance at any frequency of an electro-magnetic speaker from a plot of its electrical impedance measured when the speaker is loaded by a closed air column of variable length. The present article applies this method to a dynamic microphone, yielding pressure sensitivity at lower audiofrequencies and providing a means of calculating microphone mechanical impedance and other characteristics. Improvement in accuracy which may be achieved by proper choice of area for closed air column is discussed.
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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.