Shallow Water Test of the Theory of Layered Wave Guides

Quantitative agreement between theory and experiment has been secured for the acoustical radiation field of a simple harmonic point source of known power output, at low frequencies in shallow water. The experiment covered the range of frequencies of 88–148 cps in water 22.6 m deep in a location on the Atlantic seaboard. All instruments were calibrated. Absolute sound levels and details of mode interaction agree quite well with those predicted by the guided wave solution for a three layered liquid half space, proper account being taken of locally measured mode attenuation coefficients. These are small and are essentially introduced into the undamped theory in a posteriori, phenomenological fashion. Emphasis is given to the importance of correctly determining the acoustical parameters of the various layers, and it is shown that minor changes in these may produce effects sufficient to destroy agreement between theory and experiment. The use of various criteria, and in particular of dispersion and mode‐interaction wavelengths is illustrated in this connection.