High Frequency Sound Waves of Small Intensity and their Biological Effects

R. W. WOOD and one of us (Loomis) have described (Phil. Mag., 4, 417; September 1927) certain physical and biological effects observed with high frequency sound waves of great intensity. To obtain this great intensity, high potentials (of the order of 50,000 volts) are required, and the oscillating piezo-electric quartz crystal must be operated in an oil oath. This method is not suitable for observing biological material under a microscope.