Finite-amplitude standing waves in rectangular cavities with degeneracies and weakly-perturbed walls Article Swipe
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· 1978
· Open Access
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· DOI: https://doi.org/10.1121/1.2004163
· OA: W2038308026
It was observed and reported in an earlier paper [“Finite-amplitude standing waves within real cavities.” Alan B. Coppens and James V. Sanders, J. Acoust. Soc. Am. 58, 1133–1140 (1975)] that when there was a degeneracy involving any normal mode stimulated by finite-amplitude distortion of a driven normal mode, and a normal mode which could not be so stimulated, energy was coupled into the “forbidden” normal mode. At that time no quantitative explanation could be advanced. Subsequent work analyzing the effects of weak perturbations of the boundaries of an otherwise ideal rectangular cavity has shown that it is possible to stimulate “forbidden” degenerate normal modes through the perturbation corrections to the ideal normal modes resulting from the boundary irregularities. This coupling is important only when the eigenfrequencies of the normal modes in question are very close together. Under certain conditions the amplitude and phase of the “forbidden” normal mode can be obtained by a relatively simple calculation after the calculations for the finite-amplitude standing wave in the absence of the degeneracy have been obtained.
