Sound velocity measurements in spermaceti oil under the combined influences of temperature and pressure

Sound velocity was measured in samples of spermaceti oil from the head of a 15.6 m male sperm whale under varying temperature and pressure. Velocities were measured at stable temperatures between 22°C and 38°C, while pressure was increased from 0 to 90 atm. The temperature range encompassed those likely to occur in the head of a sperm whale, and the pressure range simulated conditions experienced during a dive to 900 m. Measured sound velocities ranged from 1390ms−1 to 1540ms−1 (±4ms−1). Velocity increased linearly with increasing pressure and decreased non-linearly with increasing temperature. There was no sudden change in sound velocity as the oil changed phase from liquid to solid. A least-squares multiple polynomial regression analysis produced a practical equation for the prediction of sound velocity in spermaceti oil as a function of temperature and pressure.