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304 pages, Hardcover
First published January 1, 2009
Sound is nothing more than changes in air pressure....As sound waves travel past snow, they momentarily increase the air pressure, forcing air into pores between snowflakes and ice crystals. As the pressure of the sound waves drops, the air moves out of the pores. The air is moving in and out a hundred times per second at a low pitch, five thousand times a second at a medium pitch, and eighteen thousand times a second at a high pitch, near the edge of human hearing....At warmer temperatures, it is more of a crunching sound, but near zero the pitch increases. It becomes more akin to the sound of fingernails on chalkboard. The crystal structure is stronger. What we hear is the sound of ice crystals being crushed and torn. The screeching is the sound of hydrogen bonds unbonding under the weight and movement of our skis.