The trouble with the sort of materials used in condoms is that they are inherently stretchy. Under any sort of pressure (more than a quite small depth of water) the material presses through any holes and either (a) rips or be (b) comes into contact with the diaphragm which is potentially almost as big a disaster. That's why the first DIY hydrophone I linked to uses an electret capsule immersed in oil in a canister. I have uses both condoms and cling film to waterproof microphones but only really for splash proofing. For those situations you can measure the mic before wrapping and after so that compensation can be made for the inevitable resonances. Probably not possible for underwater systems without the the same problems of needing a calibrated source and a lot of underwater space which, given the fact that it probably won't be possible to use the assembly at any sort of depth, is not going to be easy.
Dave PS The wackiest thing I ever sealed a microphone for (with cling film) was to listen to worms under the ground for a biologist who was trying to find a way to assess the number of worms in a given volume of soil without crushing them up with the soil and extracting the (now dead) biological material. On 19 February 2013 17:48, Martin Leese <martin.le...@stanfordalumni.org> wrote: > Fons Adriaensen wrote: > >> Don't know what Len will think of it, but putting a Tetramic >> (or any such mic) in a plastic bag isn't likely to produce >> anything usable. Basic problem is that the acoustic impedance >> of water is around 3400 times higher than that of air, so the >> water/air interface will reflect almost all energy. You need >> a transducer that is more or less matched to the acoustic >> impedance. > > I have read that the standard trick is to use a > condom. However, I puzzle whether this would > work with a Tetramic. > > Regards, > Martin > -- > Martin J Leese > E-mail: martin.leese stanfordalumni.org > Web: http://members.tripod.com/martin_leese/ > _______________________________________________ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound -- As of 1st October 2012, I have retired from the University, so this disclaimer is redundant.... These are my own views and may or may not be shared by my employer Dave Malham Ex-Music Research Centre Department of Music The University of York Heslington York YO10 5DD UK 'Ambisonics - Component Imaging for Audio' _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
