The underwater sounds of falling snow. Free

It was discovered by Scrimger [Nature 318, 647 (1985)], rather by chance than design, that snow falling into a large fresh water lake in British Columbia generated a noise level significantly above background. The underwater sounds produced by falling snow in small water‐filled containers has been examined and it has been discovered that some snowflakes on impact produce a unique acoustic signature that varies widely in amplitude and frequency, but varies little in the envelope of the pressure‐time history. Furthermore, there is always an initial growth period followed by a decay that has the damping characteristics of an oscillating gas bubble. The average power spectrum of several traces has been measured and a broad maximum was found that extends from a few tens of kilohertz out to the cutoff frequency of our hydrophone−about 125 kHz. Explanations will be presented for the origin of this unique acoustic signature. [Work supported by ONR.]