An equation is presented for sound absorption in sea water as a function of frequency, temperature, and pressure based on laboratory data. The equation includes contributions to absorption due to boric acid, magnesium sulfate, and water. The effect of pressure on sound absorption due to magnesium sulfate and water has been treated differently than in the Schulkin and Marsh equation. At 4°C our results for absorption at frequencies from 10–400 kHz and pressures up to 500 atm are substantially lower than those calculated from the Schulkin and Marsh equation.

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Chemical sound absorption in sea water cannot be considered the sum of independent relaxation processes because many equilibria have common ions. Effects of coupling on the MgCO30 and MgB(OH)+4 relaxations can be explained as simple buffer reactions that equilibrate rapidly and follow the slower reactions. The B(OH)3 relaxation, however, is explained by a different mechanism involving exchange with the HCO3−/CO32− system.

Resonator measurements in synthetic media show that sound absorption in seawater is caused by chemical relaxations involving B(OH)• and MõCO• in addition to MõSO 4. The MgCO• relaxation can be modeled as a two-step MõCO• ion-pair association in which a monomolecular step controls the absorption process. The B(OH)• relaxation involves a similar two-step association of the B(OH)• ion in which interactions with the oe H buffer system play a crucial role. A number of other relaxations are observed, but their contributions are negligible under seawater conditions.