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Treebeard's Stumper
28 September 2001

The Sound of Boiling Water

Put a kettle of water on the kitchen stove and listen to the sound of boiling water. That peaceful sound tells a story. It starts low and grows louder and harsher as the water heats up. Then the sound becomes softer just before your water starts to boil and make steam. Why is there that brief moment of "calm before the steam" that lets you know your water is ready even before the whistle? What about boiling water in space on the International Space Station (ISS) with a normal atmosphere but no force of gravity to distinguish between up and down?

That boiling kettle hides real mysteries. What is boiling? It's not just the state change of liquid water to vapor. That happens all the time as water evaporates, with no sound at all. Boiling is something else. Why does boiling water make any sound at all? Take the lid off and peer inside (with eye protection!) to discover the details.

I made a six minute MP3 recording (750K) of the sound of boiling water from start to finish. It's a simple mono recording encoded as the lowest quality mp3, but you can hear all the details. The background hiss is the gas in my kitchen stove. Listen to those interesting growls and rhythms!

The "calm before the steam" is subtle, from around 4:15 to 4:40 in the mp3. If you listen with Winamp, you can get a realtime oscilloscope or spectrum analysis. Richard Horne's Spectrogram program is another useful tool.


Recording the sound of boiling water...

Answer


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Copyright © 2001 by Marc Kummel / mkummel@rain.org