Why Does A Frozen Lake Sound Like A Star Wars Blaster?

Dec 21, 2016
Originally published on December 23, 2016 11:07 am

This winter brings the latest installment of the Star Wars franchise, full of familiar costumes, familiar villains, and the familiar "pew pew pew" of space guns. But you can skip the movie theatre and still hear those iconic blaster sounds if you visit a frozen lake.

Cory Williams discovered this natural phenomenon back in 2014, when he moved from California to Alaska. He tried skipping rocks across the icy surface of Edmonds Lake, just up the road from Anchorage. His YouTube video of the space age twanging that ensued was viewed 11 million times.

This year, Williams returned to Edmonds Lake and made another discovery. The lake was singing on its own. Why? And how? The latest video from Skunk Bear, NPR's science youtube channel, reveals the origin of that iconic sci-fi sound effect and explains why it can be heard every year in the frigid wilds.


Got your own science-y questions for us? Use this form to send them our way. We'll do our best to answer on Skunk Bear's YouTube channel.

You can follow Cory Williams' Alaskan adventures on his YouTube channel, LiveEachDay.

Copyright 2017 NPR. To see more, visit http://www.npr.org/.

ARI SHAPIRO, HOST:

Whether it's snowy and cold where you are or not, it is winter, and so we bring you a story about the wintriest of things, ice - specifically, since this is radio, the sounds that ice makes. And there's actually a lot of them, from this...

(SOUNDBITE OF ICEBERG COLLISION)

SHAPIRO: That's icebergs running into each other. And then there's this - shards of ice on a lake.

(SOUNDBITE OF ICE SHARDS CHURNING)

SHAPIRO: There's even a guy from Norway who makes musical instruments out of ice.

(SOUNDBITE OF MUSIC)

SHAPIRO: And here's one more sound that ice makes. We're going to discuss it with NPR science reporter Adam Cole, who runs our YouTube channel Skunk Bear. Hey, Adam.

ADAM COLE, BYLINE: Hey, Ari.

SHAPIRO: What is this sound?

COLE: So you're not going to believe this, but this is actually the sound of a frozen lake.

(SOUNDBITE OF FROZEN LAKE CHIRPING)

SHAPIRO: It sounds like a loon or some other bird on a lake. What is actually happening there?

COLE: So this was captured by a YouTuber named Cory Williams. He's over on the channel Live Each Day. And he went to this lake in Alaska and tried skipping rocks, and it produced this weird sound. He gets really excited about it.

(SOUNDBITE OF ARCHIVED RECORDING)

CORY WILLIAMS: (Laugher) Dude, it's so cool. Who needs "Star Wars," Dude?

COLE: He's right. It does kind of sound like those "Star Wars" blasters, right?

(SOUNDBITE OF FILM, "STAR WARS: EPISODE IV - A NEW HOPE")

SHAPIRO: OK, so what actually is going on? How does ice make this "Star Wars" blaster sound?

COLE: So this is something called acoustic dispersion. If you take a simple sound like a rock hitting ice...

(SOUNDBITE OF ROCK HITTING ICE)

COLE: ...It's made up of lots of frequencies. You've got the low notes...

(SOUNDBITE OF ACOUSTIC LOW NOTE)

COLE: ...And you've got the high notes...

(SOUNDBITE OF ACOUSTIC HIGH NOTE)

COLE: ...And everything in between.

(SOUNDBITE OF ACOUSTIC MID NOTE)

COLE: And as they pass through the ice, the high notes actually travel faster, so they hit your ear first. And then you hear the low notes.

(SOUNDBITE OF ACOUSTIC DISPERSION)

COLE: So let's hear that a little bit faster.

(SOUNDBITE OF ACOUSTIC DISPERSION)

COLE: So you can sort of start to hear that - right? - that pew (ph) sound we heard from Cory Williams.

SHAPIRO: Yeah.

COLE: But it turns out you actually don't even need to hit the lake with a rock. The lake can make that sound by itself. Here's a recording from sound artist Andreas Bick.

(SOUNDBITE OF FROZEN LAKE CHIRPING)

SHAPIRO: And what are we actually hearing here?

COLE: So that's the ice expanding and contracting so much that it has to buckle and crack, and it creates those vibrations spontaneously.

SHAPIRO: So if I go to a frozen lake and it doesn't happen to be buckling and cracking and making those vibrations spontaneously, can I just throw a rock and hear this sound?

COLE: You might be able to. It sort of depends on how thick the ice is. It has to be thin enough that it can start vibrating.

SHAPIRO: But also thick enough that it won't just break through the ice and sink to the bottom of the lake.

COLE: That's right.

SHAPIRO: NPR's Adam Cole - you can watch his video "Singing Ice: A Star Wars Story" at youtube.com/skunkbear. Transcript provided by NPR, Copyright NPR.