the sound of skates on very thin black ice

minipost

A reader pointed to this video and asked what's going on:

I’m pretty sure the sound is from an acoustic surface wave on the ice.  A thin rigid sheet is very efficient at transferring acoustic energy.  When the skater strikes the ice with a thin skate blade an impulse is generated.  The ice responds with a very rich range of frequencies (think about Fourier transforms if you have some math under your belt).  In ice the speed of sound is frequency dependent - higher frequencies move faster. A ring of energy moves out from the skate strike, widening as it moves with higher frequencies leading the pack.  The vibrating ice shakes the air as it moves creating sound that travels through the air. By the time it gets to you there is that characteristic star wars sound .. the high pitch that rapidly drops in frequency.  You may hear the air traveling sound later.. but it will be much weaker compared to the very efficient ice transfer.  

It won’t work with thick, bubbly or cracked ice ..  you’d really want black ice.  

If you’re near a lake and get a nice sheet, try throwing a rock out on the ice ..  You should get the same effect.  

 

Comments

[Craig Treleaven]

I suspect that hockey skates would make a sound rather different from that in the video.

[steve crandall]

>I suspect that hockey skates would make a sound rather different from that in the video.

It should be about the same. The FT of the impulse when the skate hits is what generates the rich audio spectrum. If you managed to strike the ice very gently it would be different.