[music-dsp] underwater sound
Bram de Jong
bram at smartelectronix.com
Mon Jun 14 09:40:33 EDT 2004
On Mon, 14 Jun 2004, Nicklas Marelius wrote:
> Just curious as to what your thoughts are on audio playing underwater.
Aah you'er lucky as I did some info-gathering on the subject:
* most important fact is that your ears are useless underwater: the
impedance of the membrane in your ear matches the impedance for air, but
not for water. Under water you hear with your BONES!
You can test this in a swiming pool: take something metal with you nd ask
a kried to bang it against the pool walls. You can close your ears with
your fingers, but it won't make any difference.
* a result from the above is that you can't hear any low tones under
water. Think of it like a high-pass filter on anything. This also results
in loss of dynamics.
* the high tones -not being obstructed by anything- will sound VERY clear
and almost perfect -so I've read-
* audio is mono only under water: sound travels a lot faster under water,
and as your ears rely on phase differences -which are a lot smaller under
water due to the speed-
* swiming poolar are VERY bad audio environments: hard walls, VERY
rectangular... It's a big reverberation tank. However sound travels
faster, so you have to scale dimentions.
* The only way to play audio under water is by using specialised speakers,
with impedance matched to the impedance of water! (called hydrophones)
* sound reflecting on the surface of water seems to have little effect on
sound, except if we're talking ocean-size waves. As far as I've read they
introduce a sort of fm-modulated effect.
* As a result of the impedance of water - I think - it's hard to make
sound under water without the right equipment, but this has an advantage:
if you DO have the right equipment all OTHER sound is completely drowned
-pun intended- by the audio from the speakers: you have creastal-clear
audio, so no anoying truck-passing-by sounds like you would have in
your home ;-)
Summary: sticking your head in a bucket ain't gonna work ;-) It would be
funny though, so please do so, and send us some pictures.
Ah, and, could you add all of this to the musicdsp.org Wiki ;-)
(after others have corrected / added)
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