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The value of sound velocity in water at temperatures above 212øF is needed for the use of acoustic devices, such as flowmeters or level meters, on water at these temperatures. The method consisted of heating water to temperatures above 212øF under pressure; propagating a constant frequency sound signal through it, and using a phase meter to detect changes in wavelength due to changes in sound velocity. The change in sound velocity was computed from the change in wavelength. The value of the sound velocity was obtained by adding the measured change to previously known values below 212øF. It was found that the velocity of sound in water decreases much more than was anticipated from extrapolation methods, at temperatures above 212øF. The measurements show that the sound velocity decreases monotonically from 5066 ft/sec at 210øF to 3230 ft/sec at 550øF. SUMMARY ATER was confined and heated under pressure to temperatures above 500øF. A phase meter was used to detect increments in wavelength of a constant frequency sound signal, propagated through the water, whose temperature was slowly changing. From the increments in wavelength, the increments in sound velocity were calculated.The measurements were started at a temperature for which the sound velocity is well known (below 212øF). Sound velocity at higher temperatures was obtained by successively adding the calculated increments to the sound velocity corresponding to the initial temperature.

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Since sound propagation is an adiabatic process, a temperature fluctuation accompanies the sound wave in media for which the specific heat ratio is greater than unity. If the equation of state and the sound field are known, this temperature fluctuation may be related to the intensity of the sound wave. A thermometer capable of measuring fast, small-amplitude temperature variations is described. Its output is calculated for the case of plane, sinusoidal sound waves in an ideal gas. Its use as a microphone and sound intensity meter is then considered.

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