Topic: Hydrophone for $20

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OK, I am back, last time I made some cheap binaurals with a set of Panasonic WM-61A capsules (Canadian eBay supplier here @ $1.50 USD per capsule).

Original post on $20 binaurals here

I had some capsules left over, so I decided to make a stereo hydrophone.

I simply did the same as last time, but retained the headphone casing. I Filled them with silicone then drew the capsule back into it with the cord, then wiped the excess flat over the top. Water-tight!

Air conduction is really still quite good...but now the mic capsule is in complete mechanical contact with the casing it picks up physical contact brilliantly, this is exacly what I want for the hydrophone applicaton.  I have made the L and R mics on different length cables about 4X the width of a normal ear spacing to compensate for the faster conduction of sound in water.

Sink test - mic laying underwater in sink, plug pulled

I'll go down to the sea tomorrow and toss them in. I'll post the result here.





...oh and one confession, it was only $6 but I feel pretty guilty...they didn't have anything smaller...



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 actually hear underwater, but should create a more interesting stereo effect.

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[nihilistic0]

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Thanks for letting me know, fixed here?

and here too?

digifish

[digifish_music]

thats great! +t

do the toilet next, please!

My wife has already sternly warned me to stay away from all ter toilets..as soon as she saw what I had made

...but the urge to know what it sounds like the other side of the S bend is tempting 

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[Eigenklang]

thats great!

I really start thinking about building a pair of these and pulling some underwater tapes in my next holiday. But building a really water resistant case for diving with my r09 will be hard.

I was never able to fully enjoy my underwarer trips sonically because diving is quite loud (the air bubbling out of your mouthpiece passes your ears which is REALLY loud).

[Church-Audio]

thats great! +t

do the toilet next, please!

\
I dont think that's a good idea what if the mics get flushed down the toilet and they take the recorder with them? hey that could be an interested journey to record. Kinda like mutual of Omaha's wild kingdom. * I am really dating my self here * "Today we are going to go where no man has gone before with a pair of mics and a recorder lets see what happens"

Chris

[baustin]

Sink test - mic laying underwater in sink, plug pulled

i could listen to this all day!

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OK here's the first field test...brilliant!

You can hear the snapping of marine crustaceans.

And I got one boat arriving.

Geolocated ...

Click here to see satellite image

Pics...






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[dennisrtyler]

too cool

[JD]

OK here's the first field test...brilliant!

You can hear the snapping of marine crustaceans.

And I got one boat arriving.

Thats pretty cool!

[boojum]

A tape geek with silicone is as dangerous as a programmer with a screwdriver: beware!   Way to go!   

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A tape geek with silicone is as dangerous as a programmer with a screwdriver: beware!   Way to go!   

When the guy with the boat pulled up I got some strange looks...

Me: Looking up - "It's a Hydrophone..."
Boater: "I hoped it was something like that...otherwise I'm ready for a quick getaway
Me: "Yeah, wierdo on the dock, run-away!"



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[F.O.Bean]

Awesome!!! Plus T for the creativity. I would like to buy a pair for recording underwater sounds(calm water) so I can make a CD-R of it to play while I go to sleep Maybe after XMAS I can afford a set I will def be in touch.

BTW, how are these powered? Just plug-in-power? If I cant apply phantom to them, I dont know if I can make them work with my SD 722 tho

Either way, very cool idea, and the sounds of the sink were def my favorite. the boat and lake samples were very harsh on the highs. Is that the usual case or just because there were boats around? Because your sink sample was damn near perfect balance wise with the treble/mids/highs for being in water and it wasnt nearly as harsh as the lake samples I am def impressed tho. And for $20.00, you cant beat that with a stick I bet you were a bit scared the first time you put them in the water, ehh? They look good too.

Have a Happy Holiday my friend!

Bean

[digifish_music]

BTW, how are these powered? Just plug-in-power? If I cant apply phantom to them, I dont know if I can make them work with my SD 722 tho

Either way, very cool idea, and the sounds of the sink were def my favorite. the boat and lake samples were very harsh on the highs. Is that the usual case or just because there were boats around? Because your sink sample was damn near perfect balance wise with the treble/mids/highs for being in water and it wasnt nearly as harsh as the lake samples I am def impressed tho. And for $20.00, you cant beat that with a stick I bet you were a bit scared the first time you put them in the water, ehh? They look good too.

Thanks for the kind words. The snapping shrimp and boat sounds are about right, that's what it would sound like if you stuck your head under-water there. Shrill/sharp. I threw them in the surf outside the boat harbor and it was very different, more bubbly and soft...recordings later...I also need to extend the cable.

They are using the plug-in power from the R-09, I was more worried about some fish/squid coming along and grabbing the hydrophone and dragging my R-09 in  I was compltely confident in the silicone-encased capsules...no problem there.

BTW: Here's what the shrimp sound like 32 x slower...

http://freesound.iua.upf.edu/samplesViewSingle.php?id=45439 (click on the black play arrow, top left of the sound display)
 
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[digifish_music]

I just found this Canadian eBay supplier with over 2000 Panasonic WM-61A capsules in stock @ $1.50 each for anyone interested...

Click here to see the eBay item