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    606 sounds
    276 posts
    How to make a Hydrophone (stereo!)


    Step 1. Buy some Panasonic WM-61A capsules (on eBay ~$15 for 10). NOTE: These capsules require plugin-power (a low voltage phantom standard) to work, that is 2V (min) - 10V (max) down the mic cable to work. Many units like the Edirol R-09 etc have 'plugin power'.

    Step 2. Note how small the contacts are and realize life will be much easier if you buy some cheap headphones and steal the cable. That way you end up with a nice fully formed right-angle plug but more importantly perfectly tinned/shielded wires ready to use (no cutting, wire stripping or fiddling - the key to a stress free build). $10 for some Sony cheapies, selected due to the low price and right-angled plug.

    http://www.digifishmusic.com/public/images/11-binaurals.jpg
    Step 2.5. Pop the end caps off and slide the ear-bud housings up the cable.

    http://www.digifishmusic.com/public/images/12-binaurals.jpg
    Step 3. De-solder the headphones (BTW: I dunked the unsoldered ends of the cable in a cup of boiling water to help straighten out the kinks from the knots) re-solder on the capsules (the earth is the contact with the tab in contact with the mic capsule body). I didn't even need to apply any more solder, just hold the two together, briefly touch with the tip of the iron and zap! done. The shield-wire goes to the tabbed capsule connector...this is too easy, surely something is wrong cool

    http://www.digifishmusic.com/public/images/13-binaurals.jpg
    Step 4. Test they are working.

    http://www.digifishmusic.com/public/images/14-binaurals.jpg

    Fill the ear buds with 100% silicone then draw the capsule back into it with the cord, wipe extra silicone flat over the top. Water-tight!

    NOTE: Use a product that claims to be 100% silicone. This will remain soft and flexible after curing.

    http://www.digifishmusic.com/public/images/21-hydrophone.jpg
    Step 5. Once the silicone has set test underwater
    Note: I ended up wrapping some solder around the outer casing to provide a bit more balast so that they sank quickly. Next time I will get some small lead sinkers from a fishing shop and add one or two into the casule before adding the silicone

    Remember to look for a smaller silicone tube than I used weirdhock:

    http://www.digifishmusic.com/public/images/23-hydrophone.jpg

    Enjoy! cool

    Click here to hear recordings from the above hydrophone

    Notes on binaural stereo underwater recording.

    The speed of sound in seawater is approximately 1500 meters/sec. In air it is 330 meters/sec. So in order to replicate the same temporal delays you would hear above water (for stereo imaging) you need to separate your microphones by about 4.5 times further than you would in air. Now this is not what you would hear underwater, but should create a more interesting stereo effect.

    digifish

  • avatar
    3050 sounds
    476 posts


    that's a modification of your DIY binaural, isn't ? Very cool, and the hydrophone sample you uploaded sounds ok too.
    A little question: in one of the pictures it seems the R09 displays a (minimal) mismatch in level betwen the left and the right capsule (actually I'm not that good at observing things, its just that I was looking for this). I wonder what's you experince with the Panasonics in this regard, is there much difference in output from one capsule to the next? Thanks.

    D
    EDIT: think fast of other nice mic implementations, that silicone tube will soon dry out smile

  • avatar
    606 sounds
    276 posts


    dobroide
    that's a modification of your DIY binaural, isn't ? Very cool, and the hydrophone sample you uploaded sounds ok too.
    A little question: in one of the pictures it seems the R09 displays a (minimal) mismatch in level between the left and the right capsule (actually I'm not that good at observing things, its just that I was looking for this). I wonder what's you experience with the Panasonics in this regard, is there much difference in output from one capsule to the next? Thanks.

    D

    Yes it is a modification of the binaural approach. I had been scratching my head about the best way to make a hydrophone for about 6 weeks. Yesterday, suddenly I realized the answer was staring me in the face. This is such a simple thing to do.

    The Panasonic WM61-A capsules I have been buying from e-bay have all been fairly close (closer than the pic there shows), the variation you see there is because you will notice one capsule is slightly tilted. However, careful hand matching of capsules (at least output levels) can be done and is a good idea if you are after the best result. In this case, they are destined to go underwater so I am not all that concerned.

    digifish

  • avatar
    606 sounds
    276 posts


    First field test today...worked brilliantly...

    Boat arriving with snapping shrimp
    Snapping shrimp 1
    Snapping shrimp 2
    http://www.digifishmusic.com/public/images/hydrophone-fieldrecording1.jpg
    http://www.digifishmusic.com/public/images/hydrophone-fieldrecording2.jpg
    http://www.digifishmusic.com/public/images/hydrophone-fieldrecording4.jpg
    http://www.digifishmusic.com/public/images/hydrophone-fieldrecording7.jpg

    Satisfying! smile

  • avatar
    3050 sounds
    476 posts


    smile Super-cool !!

    Now, how about some sea waves splashing?? Oh wait, please sail out and get a whale, dolphin or something!

    Being an inland guy myself, I try to build a bat detector as of http://www.btinternet.com/~mr.pentops/bat.htm. Too bad I'm sooo clumsy, likely will fail sad

  • avatar
    606 sounds
    276 posts


    dobroide
    smile Super-cool !!

    Now, how about some sea waves splashing?? Oh wait, please sail out and get a whale, dolphin or something!

    Being an inland guy myself, I try to build a bat detector as of http://www.btinternet.com/~mr.pentops/bat.htm. Too bad I'm sooo clumsy, likely will fail sad

    I definitely plan to spend some more time recording underwater...

    Bats, I found my NT4, AT3032 & SP-binaurals all worked quite well...

    http://freesound.iua.upf.edu/packsViewSingle.php?id=2655

    digifish

  • avatar
    29 sounds
    24 posts


    WOW, Wow! Thank you for the instructional pics. I am IMPRESSED. This is a winner. Simple, inexpensive and extremely functional. I so want to do this right now. Fantastic job.

    OK now - What do you think the possibilities are for building an EARTH microphone? That is, something that can be buried in the ground? I've wanted to do that for some time. I wonder if your project could work buried...

    Thanks again!

  • avatar
    606 sounds
    276 posts


    andrew1280
    WOW, Wow! Thank you for the instructional pics. I am IMPRESSED. This is a winner. Simple, inexpensive and extremely functional. I so want to do this right now. Fantastic job.

    OK now - What do you think the possibilities are for building an EARTH microphone? That is, something that can be buried in the ground? I've wanted to do that for some time. I wonder if your project could work buried...

    Thanks again!

    It would work perfectly, they are very sensitive to mechanical vibration, the specs show flat down to 20 Hz and can be rinsed clean when you are done smile

    digifish

  • avatar
    121 sounds
    1543 posts


    hey digifish...

    Was listening to your recordings and... I'm wondering about one things: sound travels so fast in water the difference in the sound between two microphones spread a few cm apart is too small (i.e. listening to it it will sound like mono) for us to hear the stereo. So, just looked up the speed in water: it's about 1500 m/s. In air it' about 340 m/s. So in order to get the same stereo effect as we land dwellers get, you should place the microphones 5 times as far apart from each other than our ears are. Let's say our ears are about 20cm apart, that would mean that in order to get the same stereo effect you should put your microphones at least 1 meter apart! And probably more if you really want some good stereo.

    I did some research about sound-in-water a few years ago because I wanted to organize an underwater electronic music festival. But there are some things I found out:

    1. your ears are totally useless under water. As the impedance of the eardrums is matched for air-impedance (unscientific: your eardrums are too floppy), you don't use your ears under water. All sound travels through your bones (cheekbone in particular) to your auditory nerves. Try this: when in a swimming pool put your ears in your fingers. You'll hear just the same. Actually you will hear better because the bones in your fingers act as resonators smile

    2. swimming pools sound like showers: a standard swimming pool is about 25m x 10m x 3m. The speed of sound is 5 times higher in water. That means that the "equivalent" size in air is 5m x 2m x 0.6m. So a swimming pool basically sounds like a small bathroom with a very long reverb time (someone hang some curtains in the swimming pool!).

    3. as a said above, you don't hear stereo under water. Try it in a swimming pool by having someone hit a metalic object against the walls. You can't locate where it's coming from. smile

    4. there is almost no bass under water for us humanoids: as sound is transferred through our bone structure and not our eardrums, we only hear the upper frequencies. So not only does it sound like an empty bathroom, it's got no bass.

    5. all underwater sound is hifi. If you play sound underwater (with underwater speakers), it will drown out (pun intended) all other sounds. So, underwater you can have a true hifi listening experience! smile

    - Bram

    Warning: if you break the rules, see my avatar. Freesound Admin, Moderator, Ex-Freesound-Coder & Benevolent Dictator For Life.
  • avatar
    606 sounds
    276 posts


    Bram
    hey digifish...

    Was listening to your recordings and... I'm wondering about one things: sound travels so fast in water the difference in the sound between two microphones spread a few cm apart is too small (i.e. listening to it it will sound like mono) for us to hear the stereo. So, just looked up the speed in water: it's about 1500 m/s. In air it' about 340 m/s. So in order to get the same stereo effect as we land dwellers get, you should place the microphones 5 times as far apart from each other than our ears are. Let's say our ears are about 20cm apart, that would mean that in order to get the same stereo effect you should put your microphones at least 1 meter apart! And probably more if you really want some good stereo.

    I did some research about sound-in-water a few years ago because I wanted to organize an underwater electronic music festival. But there are some things I found out:

    1. your ears are totally useless under water. As the impedance of the eardrums is matched for air-impedance (unscientific: your eardrums are too floppy), you don't use your ears under water. All sound travels through your bones (cheekbone in particular) to your auditory nerves. Try this: when in a swimming pool put your ears in your fingers. You'll hear just the same. Actually you will hear better because the bones in your fingers act as resonators smile

    - Bram

    Hi Bram,

    all good points. I had actually done the calculations for the equivalent stereo spread and have the mics capable of about 1 meter separation. Inter-aural distance is infact about 15 cm on average so you need a bit less than that.

    You probably missed what I wrote above ...

    "Notes on binaural stereo underwater recording.

    The speed of sound in seawater is approximately 1500 meters/sec. In air it is 330 meters/sec. So in order to replicate the same temporal delays you would hear above water (for stereo imaging) you need to separate your microphones by about 4.5 times further than you would in air. Now this is not what you would hear underwater, but should create a more interesting stereo effect."

    I have not gotten around to making a spacer but do intend to get a perspex rod (as it won't float) and tie the mics to each end.

    Really interesting stuff about your underwater rave smile

    nice post BTW all good stuff!

    digifish

  • avatar
    975 sounds
    145 posts


    Good Modification Idea. B+ ! : )

    .Killer.
  • avatar
    0 sounds
    1 post


    Wow just great! I've used Edmund Scientific hydrophones into Nagras and I bet they have nothing on this setup. Congratulations.

  • avatar
    1895 sounds
    1733 posts


    Just a though…

    Wouldn’t it be better to replace the black felt on the front of the condenser mics with tape, (e.g. electrical insulating, or duct type),
    to stop the liquid silicone entering the mic capsule and impeding movement of the diaphragm ?

    (Maybe the felt was sufficient to prevent this from happening in this case).

    Duct tape: the cure for all ills smile

  • avatar
    0 sounds
    11 posts


    about underwater music didnt they do something like that at the Roskilde festival last year?

    my cousin went there and told me something about that they had to float on their back in the water and of course with their ears below the surface in order to listen to the music, sounds cool but how to they do that? did you organize that underwater festival Bram?

  • avatar
    0 sounds
    1 post


    Someone knows if I can use also other types of capsules for the same purpose ?

    I think I can, but I'd like to know it before putting the silicone inside tongue

    anyway great idea!

  • avatar
    17 sounds
    55 posts


    My first real taste of experimental music was going to an underwater concert by Michelle Redolfi when I was 14; about 14 years ago. My dad collaborated on the software side. Good times smile

    I remember the sound as being very clear and compelling, but my listening wasn't particularly critical at the time.

    I've been thinking about buying or making a pair of hydrophones (partly to go with my underwater camera, which is fun). Might give this method a try.

    Cheers!

  • avatar
    527 sounds
    651 posts


    Thank you Digi, you inspired me as well.

    Inserting image bust?

    http://www.flickr.com/photos/benboncan/5375984110/

    "I love deadlines. I like the whooshing sound they make as they fly by." Douglas Adams
  • avatar
    18 sounds
    456 posts


    Benboncan

    Inserting image bust?


    Because you're not linking to an image wink

    http://farm6.static.flickr.com/5125/5375984110_e86c9eb712.jpg

  • avatar
    527 sounds
    651 posts


    Thank you.What did I do wrong then?

    "I love deadlines. I like the whooshing sound they make as they fly by." Douglas Adams
  • avatar
    18 sounds
    456 posts


    The url you put inbetween the img tags point to the flickr webpage, not the image on that page. They have an easy function, there's the 'Share' button at the top of the screen, click it and you get the option to get the bbcode used to insert the image.

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