The Origin of Sound Absorption in Water and in Sea Water

The absorption of sound in water and in sea water has been measured in the frequency range 120 kc to 1000 kc. The fresh water values were obtained in a lake; the sea water values in the ocean. The fresh water absorption values when extrapolated as the square of the frequency are in agreement with previous values measured in the laboratory at considerably higher frequencies. It is shown that the observed absorption of water has its origin in viscous dissipation; the calculated values for the absorption agree with the observed if recently measured values for the dilatational viscosity as well as the shear viscosity are included in the calculation. The absorption processes in sea water are different. At frequencies below 100 kc the absorption is about 100 times greater than in pure water. Above 1 megacycle the absorptions are similar. It is shown that this behavior can be accounted for by introducing a relaxation mechanism with a relaxation time of 10−6 second. The nature of the relaxation mechanism is not k...