SNOW SCREECHING ON WATER. With its ability to create muffled winter landscapes, snow is usually associated with quiet. When the white stuff falls on a body of water, one would expect it to be just as silent, since it doesn*t make much of an impact. But as researchers have discovered, it unexpectedly creates high-pitched screeching sounds that can sometimes disrupt underwater sonar experiments. Investigating these sounds, which last for roughly a ten-thousandth of a second, Larry Crum of the University of Washington (206-685-8622) and his colleagues implicate air bubbles as the source of snowflake noise. According to their explanation, the snowflake's presence on a water surface creates capillary action (the attraction between a liquid and solid surface), causing water to rush upwards. The upward flow of water either generates air bubbles on its own, or unleashes air bubbles in the snowflake as it melts. The bubbles oscillate as they reach equilibrium with their environment, creating sound waves of up to 200 kilohertz--out of the range of human hearing (which stops at 20 kHz) but potentially audible to dolphins. Researchers have been known to shut down sonar surveys of salmon population during snowfall because of these sounds. (Select Article, Journal of the Acoustical Society of America, October 1999; see also New Scientist, 25 December 1999.)