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December 14, 2009

Alfred M. Mayer - Pioneering Acoustics and the Invention of the Topophone

Alfred M. Mayer, Distinguished Physics Professor at Stevens Institute of Technology from 1871 – 1897, was the first to devise methods to measure the intensity of sound by nonelectrical means. He used the term “pendulum vibration” for simple harmonic motion, and his experiments with ticking clocks and soundproofed rooms show that one sound could be obliterated with a second lower-frequency sound. He was also the first to discover the phenomenon of masking, in which a lower pitched sound could obliterate a higher-pitched sound even if the latter was intense.

Highlighted in the July 3, 1880 issue of Scientific American, Alfred M. Mayer’s topophone garnered widespread attention for its ability to quickly and effectively locate the exact direct and position of any source of sound. An excerpt from the Scientific American article describes his patented device:

"The topophone consists of two resonators (or any other sound receivers) attached to a connecting bar or shoulder rest. The sound receivers are joined by flexible tubes, which unite for part of their length, and from which ear tubes proceed. One tube, it will be observed, carries a telescopic device by which its length can be varied. When the two resonators face the direction whence a sound comes, so as to receive simultaneously the same sonorous impulse, and are joined by tubes of equal length, the sound waves received from them will necessarily re-enforce each other and the sound will be augmented. If, on the contrary, the resonators being in the same position as regards the source of sound, the resonator tubes differ in length by half the wave length of the sound, the impulse from the one neutralizes that from the other, and the sound is obliterated."

The above figure shows a portable style of the instrument; for use on ship-board it would probably form one of the fixtures of the pilot-house or the “bridge,” or both. In most cases arising in sailing through fogs, it would be enough for the captain or pilot to be sure of the exact direction of a fog horn, whistling buoy, or steam whistle; and for this a single aural observation suffices.

 

Source: stalactite chandelier


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