A two crystal interferometer for rapid measurement of sound velocity in liquids and soft animal tissues is described. Velocities can be determined to within three parts per thousand with a path length of a few millimeters. The frequencies used are 1, 2, 4, 12, and 36 mc. Temperature is controlled to 0.1°C. A phase comparison method is used for wavelength incorporating dual heterodyne reduction to audio‐frequency with presentation as a Lissajous figure on an oscilloscope. Results are given for a few mammalian tissues showing the precision and reproducibility of measurements.