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dp
04-27-2010, 10:08 PM
Following the Maui thread to Maui on the web I came across whale sounds which led to other under water sounds which brought me to this site and some really fun links that continue to waste my time. But in a good way.

Have a listen: http://silentlistening.wordpress.com/2008/05/09/dispersion-of-sound-waves-in-ice-sheets/

Evan
04-28-2010, 12:35 AM
I haven't listened to the audio yet but I know what it sounds like. Back in the 70s we had a cabin on the shore of Puntzi Lake. We went out one spring just in time for the breakup of the ice that weekend. It often happens all at once. The lake can be covered in ice and 2 days later almost completely clear. We have also been out well before breakup.

The sound it makes as the ice cracks is unlike anything else. The crack travels fairly fast but not like a lightning bolt. It is slower and you get a triple reverb from the sound in the water, the sound through the ice and the sound in the air which all travel at different velocities. It can be LOUD too. It isn't something you have to cup your ears to hear. When the ice is really moving around because of wind the sound can be almost continuous and loud enough to interfere with conversation.

dp
04-28-2010, 01:12 AM
And this showed up today on the APOD site, to add to the noise, er, coincidence:

http://antwrp.gsfc.nasa.gov/apod/ap100427.html

Dan Dubeau
04-28-2010, 01:23 AM
Reminds me of ice fishing at night. Standing out on the lake in the pitch black, with no wind, you can not only hear the ice crack, you can feel it under your feet.

dp
04-28-2010, 01:55 AM
Kind of makes me wonder what kind of terrestrial noises a person would hear by dropping a hydrophone into a swimming pool or pond, frozen or otherwise. With digital audio processing widely available now it would be a simple thing to translate the sub-audible frequencies to something we can hear.

I once hammered some probes into the ground and attached them to my Tektronix oscilloscope and was surprised at both the DC and AC signals I picked up.

There's a lot of stuff going on out there.

KIMFAB
04-29-2010, 01:38 AM
I love going to Bryce Canyon in the spring and listening to the snow melt.

darryl
04-29-2010, 02:20 AM
I have a 3 ft diameter styrofoam disc with a groove in the rim which is wound with copper wire. The coil is coupled to a sensitive amplifier circuit which also is a steep 60 hz notch filter. Runs on a 9v battery and picks up radiated audio frequency signals. Pretty interesting what you can hear at times. Sometimes almost nothing, other times strange tings and plinks, sweeping frequencies, bloinks- it's hard to describe what some of these sounds are like.

I've heard the lake ice sounds first hand, that's pretty cool. A group of us were walking across the lake listening to this. I wanted to come back with an audio amp and try to get some feedback going, but never did. It would have been interesting to propagate some sympathetic vibrations through the ice and see what happens-

Evan
04-29-2010, 04:24 AM
One of these days I am going to get around to building a hetrodyne ultrasonic bat listener. By beating the microphone signal with a 20khz reference the next 20 khz can be brought down into the audible spectrum. The current crop of tiny electret microphones should be ideal for this.

There are all sorts of ultrasound sources to be heard, especially at night. Not only do bats use echolocation but many of the prey such as moths emit false echos to confuse the bats. Mice communicate with ultrasound as do many rodents including squirrels.

Check out Howling Mice: http://www.google.ca/search?hl=en&q=howling+mice+&meta=&aq=f&aqi=&aql=&oq=&gs_rfai=

Jim Shaper
04-29-2010, 05:35 AM
I thought this site already was an internet time waster. :D

I've gotta admit, youtube "cnc crash" is good for some guilty pleasure too.