Speed of Sound in Fluorocarbon Liquids

Abstract

Fluorocarbon liquids are used as acoustic lens mediums in underwater sound focusing devices; therefore, the speed of sound in them as a function of pressure is essential information for the designer who wishes his equipment to operate in the ocean depths. Accordingly, sound speeds were measured as a function of temperature and pressure in a number of liquids likely to be used for this purpose. The temperature and pressure range of measurement covered was that which might be encountered in the ocean : 0° to 30°C and 0 to 700 kg/cm2. In addition, values were obtained for Rao's constant and Beyer's parameter of nonlinearity, B/A. The unusually high values of B/A found ofnonlinearity,in the fluorocarbon liquids is consistent with their low sound speeds and suggests that these liquids, or other low-velocity materials, may be of some use as a high-efficiency medium for parametric sound generation. The specific liquids investigated were Fluorolube (FS-5); FC-43, FC-75, and FC-88 (all fiuorinated hydrocarbons); FC-114B2 (1,2 dibromotetrafiuorethane) and Freon-C51-12 (perfluorodimethyocyclobutane) ; and Freon 113 (Freon TF, MS-182). The sound speed was determined using the method of Greenspan and Tsehiegg, which measures the pulse repetition rate necessary to overlap rf pulses of adjacent echo trains.