Ice sounds explained

[Don Boucher]

Hello,

I loved Howard's mysterious bird-like sounds from the abandoned quarry at McDonald Forest. It reminds me of when I discovered this phenomenon as a boy in rural Pennsylvania. There was a pond in our neighborhood and one winter, my brothers, a neighborhood friend and I decided we would see if we could throw rocks high enough to crack the pond ice. We didn't crack the ice but the sound it made blew us away. It sounded like chirps and Star Wars laser blasters. We spend the better part of an hour making different sounds by throwing things onto the ice.

Howard's sound is probably the pond ice. It could either be rocks and pebbles falling onto the ice from the quarry wall above or just the ice itself fracturing and flexing as it expands or contracts during changing temperatures. The size of the body of water affects the outcome of the sound and I gotta say that Howard's recording did remind me of Swainson's Thrushes. In 4 months, this very spot will be surrounded by the sounds of real Swainson's Thrushes.

This YouTube video by NPR's Skunk Bear explains and demonstrates the phenomenon.

https://youtu.be/OC7_zpyqCrU

Don Boucher

Corvallis