The Age of Electroacoustics [Book Review

Abstract

This book is an fascinating read. The author does a good job of putting the study of acoustics in context within social, political, academic, and industrial environments through time. He concentrates primarily on the U.K. and Europe, with a few references to the U.S. and other countries. The Weimar Republic chapter of course deals almost exclusively with Germany during that era but that focus is acceptable as Germany was then also addressing questions as to what physics was in a broader context. When WWI began, a major shift occurred regarding the definitions of noise and sound, and the recognition of the value of studying more than musical notes as sound. The sound made by an enemy airplane was a signal to be detected, so that the bearing, elevation, and range could be determined for defensive purposes. Valuable data could also be obtained through studying the sounds produced by U-boats or long-range cannons. Suddenly what was previously ignored as irrelevant became of great interest. Noise was redefined as that which is not the intended signal. Noise abatement also moved to the forefront — making ships and airplanes quieter became very important. The implementation of electroacoustics changed the interpretation of signal characteristics, with the introduction of microphones, vacuum tube amplifiers, and visual displays. The technology of these devices was greatly advanced during WWI. The author points out a number of technical solutions to problems in electroacoustics and how they influenced the field. For example, since electronic filtering was not well developed, and microphones did not have a large dynamic range, the frequency selective Tucker’s Hot Wire Microphone was developed. Tucker’s Hot Wire Microphone, a resonant cavity with a hot wire stretched over one end whose resistance changes when vibrated by sounds at the cavity’s resonant frequency, can be made to detect sounds below 500 Hz without interference from other frequencies.