Acoustic Impedance from Motional Impedance Diagrams*
When an acoustic load is coupled to an electromagnetic transducer through a length of air column, there is a critical length at which an increment in acoustic load produces a maximum increment in electrical impedance. The method described makes use of this critical coupling to obtain an optimum precision in determining an acoustical impedance. It is noteworthy that the value of the characteristic impedance of the air column is not assumed but is directly measured.
Figures & Tables
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.