Resonance Reverberation Method for Sound Absorption Measurements

A resonance-reverberation method for measuring sound absorption in liquids from about 20 kc to above 600 kc has been developed. A single spherical glass container holds the liquid under test. The spherical system is excited with an intermittent train of continuous sound waves generated by a piezoelectric element. A second piezoelectric element detects the manner in which the sound energy dies away after the excitation stops. The time constant of this decay is inversely proportional to the sound absorption of the system. The liquid container was calibrated with liquids of known absorption to enable the separation of the wall losses from the liquid absorption. The sound absorption coefficients of 44 liquids are tabulated. Acoustic relaxations which were observed in some of the compounds studied are attributed to the perturbation by the sound wave of equilibria between rotational isomers. The application of the resonance-reverberation technique to sound absorption measurements in solids is presented.