WASHINGTON, Oct. 16 (UPI) -- Cory Williams, actor and YouTube personality, makes a living by filming videos of himself. Lately, those videos have involved exploring Alaska, and his most recent one included the discovery of the acoustic wonders of a freezing lake.
Williams' fascination with the sounds of a half-frozen lake, similar to the sound of lightsabers in the Star Wars films, can be seen in the video around the 3:45 mark.
For those in northern climes, water is regularly on its way to becoming a near solid block of ice. It happens every autumn. But in central California, where Williams grew up, huge half-frozen lakes are less common. Uninitiated to this winter weirdness or not, pings and pangs of a semi-frozen lake can be awe-inspiring.
But why does a chilly fall day spent skipping rocks across a sheet of lake ice sound like a sound studio at Lucasfilm? The answer is: acoustic wavelengths.
"I'm from Massachusetts originally, and I've heard this phenomenon often," Mark Hamilton, an acoustics professor at the University of Texas, told LiveScience. "I use this example every year when I teach our introductory acoustics course."
When a stone or object hits a piece of ice, it sends out a range of vibrations, each spreading out across the ice in all directions. The thin sheet of ice on top of a semi-frozen lake acts as a vibrating plate. And because high frequencies (shorter wavelengths) travel faster, they arrive to the ear first.
"It's as though you ran your finger from right to left across piano keys," Hamilton said.
Of course, distance must be involved, or else the delay between high and low frequencies won't be discernible. That's why skipping a rock, creating vibrations far out on the ice, is ideal.
But how did the X-wing lasers in Star Wars get their sound? Did George Lucas and company travel to Alaska? Actually, the slinking laser-like sounds were made in the prop department, by tapping an antenna tower guy-wire with a hammer. Now you know.