Sound absorption in seawater at pressures up to 307 atmospheres

Using a 100‐liter titanium spherical resonator sound absorption from 45 to 350 kHz has been measured in Lyman and Fleming seawater at 25° and at pressures of 1, 71, 188, and 307 atm. Assuming a single $MgSO4$ relaxation process, the data were analyzed for the values of the maximum absorption per wavelength, (aλ)_max, and of the relaxation frequency f_r At 1 atm $(aλ)max = (61.65 ± 0.34) × 10−6$⁠, in good agreement with that measured by Wilson and Leonard [J. Acoust. Soc. Am. 26, 223 (1954)] and by Simmons (Ph.D. thesis, University of California, San Diego, 1975). The relaxation frequency of 133 kHz is lower than those reported by Wilson and Leonard and by Simmons. At elevated pressures the relaxation frequency remained the same contrary to the increase observed by Bezdek [J. Acoust. Soc. Am. 53, 782 (1973)] in field measurements. Absorption decreased linearly with pressure according to the equation $a(p) = a(l)(1− 9.1 × 10−4P)$⁠, where P is in arm. This decrease is 25% smaller than Bezdek found but nearly the same as Fisher [J. Acoust. Soc. Am. 38, 805 (1965)] measured in 0.5 M $MgSO4$ solutions. [This research was supported by ONR, NSF and ARPA.]