A simple tutorial to do an hydrophone (aquatic microphone), step by step.
1. Mic cable (mono)
3. Piezoelectric sensor (on our video we used a 1″ piezo)
4. Plastic lids or “feet” for chairs or tables (with a diameter about 1cm bigger than piezoeletric’s diameter)
5. 1/4″mono jack plug
6. Iron washers
7. Rubber coating
8. Copper foil
11. Electric tape
3. Drilling machine
5. Hole saw (with a diameter a bit smaller than piezoelectric diameter)
6. Cutting plier
7. Soldering iron
9. Permanent ink pen
Choose a plastic lid with a diameter about 1cm bigger than piezoeletric’s diameter. In our video we used a 1″ piezo (25mm)
With a ruler mark the center of the plastic piece
Make a hole with the drilling machine and the hole saw. (The hole saw diameter should be a bit smaller than piezoelectric diameter)
On the side of the plastic lid make a hole with the drill. It’s where the mic cable will pass through.
We will use the copper to protect the hydrophone from electro-magnetic interference.
Measure the plastic lid height
Cut the copper foil as a strip with the same height.
Take the copper strip and internally cover the lid.
Fix the copper ring with electrical tape
With scissors cut a hole on the side of the ring Note: it exist a self-adhesive copper foil which could be better for this use (and easier to work with)
Position the piezo centered outside of the lid. The terminals must be seen inside the hole.
Fix it with electric tape. It will be removed on step 5.
Before soldering put 2″of thermofit on both sides of the cable.
Pass the mic cable through the lid and copper holes and solder it on piezo’s terminals : ground on the external part, positive on the internal part of the piezo.
Solder the 1/4″mono jack plug on the other side of the cable.
After soldering, reposition the thermofit and get it hot with the lighter.
Note: it would be possible to use a stereo cable to have probably better shielding. You should then connect ground to the copper foil, positive on the center and negative on the external part of the piezo.
Fill half of the lid with silicon.
Put 2 iron washers inside it. (In order to give some weight to the hydrophone)
Fill the rest of the lid with silicon.
Cut a copper foil circle, with the same diameter as the lid.
Put the copper circle on the top of the silicon, so it will get glued._ Wait until the silicon dries (about 30 minutes)
Note: you could put some weight on top of the copper foil, so it will get straighter.
Carefully remove the electric tape from the piezo.
Dip the lid in the rubber coating can and take it out very slowly.
Let it dry for around 30 minutes and repeat this step 2 or 3 times.
For a uniform rubber layer, you can turn the lid upside down while drying
Try your hydrophone and share your recording
Other nice hydrophone tutorials where we learned to construct ours:
Phase 57 give a very similar way of building a contact microphone, shield as ours, and I guess that could easily be used as a hydrophone
Zach Poff give a step by step building of a contact mic in a very easy way. With an interesting list of other places to buy some contact mic online (at the bottom of the page)
John Grzinich share here a nice way to build a DIY hydrophone
If you want to buy some, here are a few links :
Aquarian is one of the famous constructor of very good and cheap hydrophones, already very famous
Dolphin Ear is doing very good hydrophones too (a bit more expensive)
Cold Gold has a lot of different models of contact mic and hydrophone, at very good prices (including some piezo and copper foil for DIY mic)
Jez Riley French is doing and selling a few models of contact and hydrophone since a long time now (at a good price too)
Crank Sturgeon sells different models of contact mic (some are waterproof) done by himself
Monkey Sound is doing and selling a few nice models too
Geophone by LOM Audio. It is not an hydrophone, but it’s a very nice tool for contact recording
Ambient sells ones of the best hydrophones, but with a much higher price