DIY Hydrophone

A simple tutorial to do an hydrophone (aquatic microphone), step by step. Do It Yourself following each step below.

Materials:

  1. Mic cable (mono)
  2. Thermofit
  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
  9. Solder
  10. Silicon
  11. Electric tape

Tools:

  1. Cutter
  2. Scissors
  3. Drilling machine
  4. Drill
  5. Hole saw (with a diameter a bit smaller than piezoelectric diameter)  
  6. Cutting plier
  7. Soldering iron
  8. Ruler
  9. Permanent ink pen
  10. Lighter

STEP 1 | PLASTIC LID PREPARATION

_ 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.

STEP 2 | COPPER FOIL

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)

STEP 3 | PIEZO & CABLE SOLDERING

_ 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. 

STEP 4 | Silicon and iron washers

_ 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.

STEP 5 | Rubber coating

_ 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

STEP 6 | Listening

_ Try your hydrophone and share your recording 
_ Enjoy

TUTORIAL by Sara Lana & Félix Blume

Other nice hydrophone tutorials where we learned to construct ours:

If you want to buy some, here are a few links :

Missing a link to a nice DIY tutorial or another nice way of buying an hydrophone? Contact us!
https://saralana.xyz/about
https://felixblume.com/contact