[music-dsp] sounds under water...

Angelo Farina farina at pcfarina.eng.unipr.it
Sun Jan 11 08:11:01 EST 2004


Several years ago there was an underwater concert of electronic music here
in Parma, Italy, inside the swimming pool... I partecipated to this, but
most people did not manage to go equipped in such a way to enjoy the music
properly. In fact, the transducers were radiating just in the water, with
the head outside of it You could not hear anything. It was necessary to have
at least a mask and a snorkel, for eeepinghYour ears submerged, instead most
people were not equipped properly, so they did not enjoy the experience (the
electronic music was also quite questionable by itself, of course). Of
consequence, this experiment did not have any following. I do not remember
the name of the artist...
This happened more than 20 years ago...
However, I remember the maker of the underwater loudspeaker. It was a small
company located in la Spezia, Italy. They are still cative, and work mostly
under contracts with the Italian Navy, or for the NATO SACLANT center. The
company is named Tele Sub Lanterna, and they also manufacture underwater
microphones (hydrophones) and ultrasonics underwater walkie-talkies....
Regarding the different "physics", underwater there is no substantial
difference from the acoustical laws in air. You must consider, however, that
the speed of sound is approximately 1500 m/s instead of 340 m/s, so the
wavelenght is much greater, and the time delay much shorter. This has the
practical consequence that underwater an human cannot localize the direction
of provenience of the sound, because all the three localization cues do
fail: at low frequency, the interaural delay is too short. At mid
frequencies, the interaural level difference is much smaller than in air.
And at high frequency, the pinna-colouring effects occurs in a way
completely unusual for our brain, which consequently cannot employ it for
localizing.
The sad consequence of this is: no surround underwater!
Furthermore, consider that a swimming pool is a quite reverberant
soundfield. As the water sound absorbtion is very little, and the walls of
the swimming pool are usually very smooth and hard, You will be radiating
sound in a very reverberant "space", and consequently the music will sound
like in a church...
Good luck with Your project, and please inform us of any progress...
Bye!

Angelo Farina
 

> -----Original Message-----
> From: music-dsp-admin at shoko.calarts.edu 
> [mailto:music-dsp-admin at shoko.calarts.edu] On Behalf Of 
> Smartelectronix - Bram de Jong
> Sent: 11 January 2004 02:10
> To: music-dsp at shoko.calarts.edu
> Subject: [music-dsp] sounds under water...
> 
> hey guys,
> 
> 
> 
> I've long had this idea of working together with the city I 
> live in to make an under-water audio installation in one of 
> the few pools we have here...
> 
> I was thinking a multi-speaker, multi-channel emersive (pun 
> intended) audio environment.
> 
> Now the questions are simple :
> 
> 1. what apparatus can be used? I know there exist under water 
> speakers, but they would probably cost a lot! Could 
> ABOVE-water transducers be used, when coupled to an object 
> that goes sub-water-level? (think metal/plastic/...
> sheets that "hang" into the pool)
> 
> 2. what difference does water make on the acoustics? Would 
> low-frequencies work? would you be able to get nice stereo 
> sounds with speakers around the pool?
> 
> 3. has anyone got experience with this sort of stuff? any 
> other pointers?
> 
> 4. have I gone completely start raving mad? ;-)
> 
> 
> Combined with propper lighting and opening the pool at night, 
> it would be quite fun to have people diving upder the water 
> to hear what's going on...
> 
> 
> 
>  - bram
> 
> 
> --
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