Have you ever heard a frozen lake sing? If you skate across a frozen lake, you may hear some incredibly eerie and beautiful sounds. Take a look at this video to hear singing ice:
When the blade glides across the ice, it creates sounds made up of a mix of higher and lower pitches. Sound moves in waves, similar to the diagram below. The diagram shows waves going up and down, but if you want to recreate sound waves more accurately, place a slinky horizontally on the floor. Push the slinky forward, and watch how the waves travel through the slinky and back towards you. The rings get closer and further apart, making what scientists call “longitudinal waves,” which is illustrated with the dots in the diagram. It’s the perfect name, since longitudinal means “length,” and the waves move along the length of the slinky! They’re also called “compression waves,” as you can see the rings get compressed, or squeezed together.
Higher notes are made up of tight waves. They vibrate faster, or in other words, are higher frequency, than lower notes. Although all sound waves usually move at the same speed no matter their frequency, sometimes the sound waves separate by higher and lower frequencies when they move through something solid, like ice. The higher frequency sound waves in this case move faster than the lower frequency soundwaves. This is called acoustic dispersion. Then, when the sound waves reach our ears, we hear the higher pitches followed by the lower pitches, which end up sounding like a “pew,” just like in Star Wars! Actually, it really is the same science used to make those laser blasts in Star Wars, except they used a radio tower’s guy wires.
If you have a frozen lake nearby, you don’t need to skate across it to hear these amazing noises. Frozen lakes will make these noises all by themselves with the right conditions, as the ice expands and contracts, sending out vibrations across the lake. Skipping rocks far across the lake can also make the same sounds.
Make your own sound effects!
If there isn’t a frozen lake nearby, you can recreate the sounds with a handleless cup and a metal slinky! This acoustic dispersion effect works in metals too, which is why you can hear similar sounds with long wires. So the metal slinky will act just like the ice, as the sound waves travel up and down it.
Place the cup inside one end of the slinky, which will make these sci-fi noises louder so you can hear them better. Hold the cup and slinky above the floor, then let go of the opposite end of the slinky so that it hits the ground. You should hear a “pew” now! Play around with how the sound changes as you move higher or lower above the ground. Then, let the slinky hang and try hitting the slinky with different objects and see if it still works! You can experiment with this and record your results in a template like below.
Record your cool sounds and share them with us by tagging us on social media!
Bonus Sounds
Ice can make similar sounds in other ways too!
Check out this video of scientist Dr. John Higgins and his team in Antarctica drop a 9-inch chunk of ice sheet down a 450 foot hole:
What does a 9 inch ice core sound like when dropped down a 450 foot hole? Like this! Credit to @peter_neff for the idea and @Scripps_Polar, @sciencejenna, @GeosciencesPU, @US_IceDrilling, and @paleosurface for the execution! pic.twitter.com/pW7LxKdbUB
— John Higgins (@blueicehiggins) February 7, 2020
If you live in an area where winter temperatures can change quickly, such as around the Great Lakes and St. Lawrence River, you may hear the same sounds during an ice quake. This happens when frozen soil or rock cracks after enough water seeps into the ground and freezes due to sudden dropping temperatures. Because ice is less dense than water, the water expands when it freezes and causes the ground to crack. Have a listen here:
