MEASUREMENT OF THE SOUND PRODUCED BY A TIPPING TROUGH WITH FRESH AND SALT-WATER

Recent experiments confirm the production of sound by breaking waves a t lower frequencies (30 to 500 Hz) with a dipole characteristic. The n oise produced has a broadband characteristic associated with the impac t and subsequent sounds that have discrete spectral characteristics. B reaking waves are known to produce bubble plumes and bubble clouds, th e dynamic evolution of which provides a mechanism for sound production . Since the initial plume and cloud have appreciable void fractions, c ompressible resonant oscillations of these structures as a whole or in parts are possible. These bubble plumes would act as compact acoustic monopole sources of sound and due to the pressure release surface wou ld have an effective dipole characteristic. Sufficient energy exists i n the initial breaking vorticity and turbulence to excite these region s and to explain measured source levels. These effects have been simul ated with a tipping trough experiment that demonstrates the production of low-frequency sound from salt and fresh water tipping trough event s. These experimental results are shown to be consistent with the theo ry of sound radiation from the collective oscillations of bubble plume s.