Unusual Observations During Speed of Sound Experiments in the Arctic in the 1820’s and their Effect on the Development of Nonlinear Acoustics
Wednesday, November 14, 1984 12:00 p.m.
David T. Blackstock
Applied Research Laboratories
The University of Texas at Austin
In 1821-22, during an exploration voyage to northern North America to try to discover a “Northwest Passage” (a quick route to the Pacific Ocean), some measurements of the speed of sound were made. The time between the flash of a ship’s cannon and the arrival of the blast wave about a mile away was measured under a variety of conditions. One series of measurements was marked by the unusual observation that the blast wave always arrived before the officer’s command to fire the gun. The apparent reversal of expected arrivals was later taken to be evidence that intense sound travels faster than weak sound. In particular, Earnshaw’s prediction that the propagation speed of a sound wave is u+c, where c is sound speed and u is particle velocity, seemed to be supported by experimental observations. Some comments about the applicability of the experiments to Earnshaw’s prediction will be given. Some alternative explanations for the reversed arrivals will also be explored.