Attenuation of Sound in Water Containing Air Bubbles Available to Purchase

Measurements of the attenuation of sound in water containing air bubbles were undertaken in order to confirm some aspects of a theory due to L. L. Foldy. Bubbles were produced by forcing compressed air through the cloth covering of several trays lying on the bottom of the Black Moshannon Lake. The distribution in size of the bubbles and the number of bubbles per unit volume were determined by photographing the bubbles and by collecting the volume of air which rose over a given area in a given time, the terminal velocity of rise being a known function of bubble diameter. The attenuation of sound was found to be very large at frequencies for which resonant bubbles were present, and much smaller at other frequencies, indicating that resonance absorption was the principal phenomenon observed. For the particular bubble distribution investigated, which contained 0.045 percent air by volume, the attenuation was found to be in satisfactory agreement with the theory and a maximum attenuation of approximately 20 db per inch was measured. Amplitude and phase fluctuations made it impossible to measure the phase velocity, but this quantity was computed from the bubble distribution.