Introduction: Underwater Microphone (Hydrophone)

Picture of Underwater Microphone (Hydrophone)

Construct a inexpensive hydrophone out of things laying around your house.

I decided to put up this instructable because (to my surprise) no one has a hydrophone instructable up yet. I made mine using a mixture of other people's hydrophone creations that I found through a google search and a bit of ingenuity.

Here's the parts that I used but it should be fairly easy to adapt whatever similar items that you can find.

computer microphone

plastic wrap

vegetable oil


knife or scissors

( I used a small spray bottle that was originally some "energy-caffeine spray")

Step 1: Breaking Down Parts

Picture of Breaking Down Parts

You are going to dissasemble the computer mic so that you have the capsule and the cord seperated, I didnt put any pictures of this up because I already disassembled them before deciding to make an instructable, but the proccess is pretty easy and is a little different with every mic.

You also should have your bottle or container taken apart.

Step 2: Cut, Strip and Connect

Picture of Cut, Strip and Connect

Using a small pear knife make a hole in the top of the lid and feed the cord through. It is important to make the hole as small as you can so it as water tight as possible.

After the cord was in I stripped the wires and connected them to the Mic Capsule by carefully twisting the wires together.

Step 3: First Test

Picture of First Test

It is a good Idea to test the connection before soldering and wrapping everything.

Plug the mic into your computer or recording device and test it.

Step 4: Soldering and Wrapping Connections

Picture of Soldering and Wrapping Connections

If your test was successful then you can solder your connections.

If it was not make sure that your wires are in the right spot and that they are well connected also check the volumes of your recording equiptment.

There are a lot of different ways that you can do this, but you need to insulate the wires so that they do not touch each other, the mic capsule, or water.

If I had access to a glue gun I would of sealed them that way instead I used plastic wrap, and indiviually wrapped the connections and then wrapped them all together.

After you do this its a good idea to test the mic one more time.

Step 5: Fitting the Capsule

Picture of Fitting the Capsule

Now you should continue to wrap the capsule with plastic wrap until the capsule fits tightly in the lid, but not so tight that you can't fit the lid over the opening of the bottle this may take some trial and error.

Step 6: Vegitable Oil

Picture of Vegitable Oil

Pour vegetable oil into the bottle until it is nearly at the top, leaving a little room for the mic capsule.
Push the lid over the bottle opening, the mic will dip into the vegetable oil and go into the bottle,

The lid should stretch and go over the bottle and create a near air-tight seal, some vegetable oil will probably come out be sure to wipe off the oil before putting it in water, you do not want any air in the bottle it should be full of oil.

I taped around the edge, where the lid was over the bottle and wrapped more plastic wrap around it to make sure it was sealed well.

It is also a good idea to seal the lid where the cord is at with hot glue or super glue.

Step 7: Done

Picture of Done

Now you can test out your hydropne, its not exactly research quality or anything but it does work, you will also want to make some sort of weight to hold it under water as it does want to float.
A key ring with some old keys works great.


Boles373 (author)2016-05-07

Hi, how can I make an underwater speaker - small one.??

danlancheros (author)2014-12-01

Hi, thanks for your post.

Does the goldfish makes any sound? what kind of sound does it make?

hra (author)2012-05-04

my I know where I can buy the Hydrophone another one???
I need ur product,
I hope u can help me,
ooowyaa,, may I know, how u know the qualification or charactrstic of some bioaccoustic signal from the fish???
thx lot

TheDugger (author)2008-06-23

Having successfully built an underwater housing out of an ammo can (see instructions on this site), I am wanting to take the next step and get clear audio. Knowing nothing about hydraphone technology, I was with you until you submerged your mic into the oil. Why doesn't that render the mic useless? What role does the oil play?

action_owl (author)TheDugger2008-12-07

the oil allows the microphone to better pickup the sound waves in the water. oil is non-conductive and therefore does not interfere with most electronic equipment:
see this oil cooled PC for example:

dosci (author)action_owl2009-09-21

thanks, but i had a problem: the mic was still working after i submerged in into oil without closing the bottle, BUT after i closed the bottle, and the extra oil licked out, the mic became dead, not functioning anymore...(i tryed with 3 mics.. and alwaiìys the sa,me..). any idea why is that happening? is it possible that this is due to an excessive pressure of the oil against the micro membrane? any suggestion?

burwuro (author)action_owl2009-01-31

Yea and the hydrophone (in my opinion) would work better if their was a membrane (idk saran wrap) so that the vibrations will be able to be picked up better. and it wont break from pressure because of the oil keeping the pressure the same.

TheDugger (author)2009-08-18

Well I finally got around to giving this a try. I lined everything up and assembled it just as instructed. I put it into the water to try and what recorded was a very faint sound of my kid's voices. I am going to give the condom approach a shot. If that doesn't work, I'll give up and buy one.

belgvr (author)2009-06-09

would be great if you put some example audio of what you have got :D

wupme (author)2008-10-19

Air ain't the problem, its just cruel to put a fish in such bowls. In some countrys (Germany for example) its actually illegal to put fish in such bowls, pet stores also don't sell them. You still can buy bowls of course, for food or decoration.... A fish needs a tank, plants, a water filter and some other fish of course. I actually got one 320 liter tank, and another 200 liter tank. And an 80 liter for raising babys.

hogiewan (author)2008-06-04

I would think a piezo disc with sealant covering the side with the terminals would work as good if not better

gege (author)hogiewan2008-10-19

I fully agree. I had seen somewhere about using an electret microphone . I did pur it in veg oil .... It worked nicely for a few hours ...Until the oil got into the work (beneath the cloth) ,then the sensitivity went way down. I did a second one to be sure and SAME thing I then used one little dynamic cartridge with a plastic cone (for resistance to oil), added an amplifier and it still work. I have ordered some piezo slabs to build into microphones(pressure transducers)they are cheap if they are not finished as full underwater microphone. The trick will be to protect from water.................

action_owl (author)hogiewan2008-06-05

true dat, I didnt have a piezo element though... I heard you can get them off of those musical greeting cards

hogiewan (author)action_owl2008-06-05

Radio Shack has them pretty cheap, but you should take them out of the casing - just be careful not to crack the crystal

Badgergirl (author)2008-06-12

ummmm, so you would use this to talk to your goldfish? SWEET!! Now all i need is a fish communicator to communicate with all the fish of the world so they can help me in my quest for world domination! Mwa ha ha ha ha ha ha ha ha ha ha :P

matt_sawyers (author)Badgergirl2008-07-10

I have the whale speech plug-in for the communicator... Created from the research from the "Finding Nemo" movie...


joking of course...

Man, I think I spent a good fifteen minutes googling around for that, haha.

lol, Find anything?

action_owl (author)2008-06-05

hmmm... never knew that, I'll get him a plant, but the bowl's gotta stay I bought him at Wal-Mart and when they gave him to me they said "good luck"... so I guess he's doing better than expected. I'm also working on an instructable for a wind powered bubbler for him.

matt_sawyers (author)action_owl2008-07-10

your always lucky if the fish lasts longer than 2 weeks when purchasing from Wally World...

labelreader (author)action_owl2008-06-10

Actually, it's a myth that bettas are "happy" in small spaces. They're shown that way in Japan because it provides a nice view of the fish, not because the fish like it. In a large tank they seem to enjoy being able to swim vigorously, and they're great in community tanks (as long as you don't put two male bettas in there together, of course).

kington99 (author)2008-06-05

you mean that they don't have a sufficient surface area to dissolve sufficient oxygen for the fish? This one obviously does, else the fish would be dead.

legendaryfrog (author)kington992008-06-09

hey man. did you know a closet has enough oxygen to keep a human alive? This isn't a matter of oxygen, its a matter of having enough space.

fib3roptix (author)2008-06-08

Im making one like yours right now..

fib3roptix (author)2008-06-08

Do you wrap the tip of the mic too????

fib3roptix (author)2008-06-07

I used a plastic shaker cup and cup a slit in the top and sealed with electrical tape + super glue. but it doesn't work as good as yours. YOURS IS AAAWWSOOME!!

Jr Hacking kid (author)2008-06-05

diegobb (author)2008-06-05

Like hogiewan says using an piezoelectric element instead of a mic will give you much better results. I made an hidrophone for a college friend, who's recording some fish sound for their final work at the university. (I'm studying electronics and he is ocean "something")
I managed to get +40 to +42db of gain with an piezoelectric (Those that comes with thats annoying christmas cards). The circuit uses two low noise op amp and the piezo. The signal from the pre amp goes to a pc, or better to a pro digital recorder. (My friend do this last).
(PS: Please, excuse my bad english.)

action_owl (author)diegobb2008-06-05

the greeting cards use the piezo electric element as the speaker for sound to come out of right? Would you be able to just wire it up as a microphone instead of a speaker and hook it too a pre-amp or is there more electrical work involved? also: would the element be able to come in direct contact with the water? (besides the wiring terminals of course) or would you have to water proof the piezo element as well? I think a Piezo Element Hydrophone instructable is really needed!

diegobb (author)action_owl2008-06-05

Yes, most of them use a piezo electric. Yes, you need to make a little smal pre amp circuit with a low noise operational preamplifier, use a fet op amp, beacuase they need very low bias current. No, i don't think that just droping the piezo element in water is a good idea. You can use some epoxy to isolate the piezo. Don't use silicon, it is too soft and act's like a high pass filter, don't use a totaly rigid material, because the piezo elements needs to move to produce electricity.

hogiewan (author)diegobb2008-06-05

piezo elements have a very high impedance, keep that in mind while designing the buffer/preamp ( another reason to use jfet opamps )

diegobb (author)diegobb2008-06-05

This is my friendThis is my friend, actually he get some money from an international institute, to expand their investigations to dolphins, based in their studies of the sound produced by the Micropogonias furnieri.

action_owl (author)diegobb2008-06-05

Very awesome diegobb, thanks for the info I am going to get to work on a piezoelectric hydrophone,and I already have a few preamps that I can use too.

jbakerathome (author)2008-06-04

Nice simple Instructable. You can use mineral oil as a substitution for vegetable oil since it can go bad after about 6 months.

Doveman (author)2008-06-04

Never heard of one. Cool though!

JowSithm (author)2008-06-04

I've always wanted to waterproof my guitar amp and a microphone and record it under water to see what it sounds like.

i make shooting things (author)2008-06-03

would be kinda cool to listen to if you could getting into the plumbing

darkmuskrat (author)2008-06-03

*bloop bloop. good instructable

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