Building a Hydrophone for the ROV


#1

I am currently working on designing a hydrophone for OpenROV. My starting point will be the following guide from NOAA.

https://swfsc.noaa.gov/publications/TM/SWFSC/NOAA-TM-NMFS-SWFSC-417.PDF

My initial thought is to use a cheap microphone and encase in a small container filled with mineral oil. However if anyone in the community has any tips, tricks, or would like to follow along and give advice feel free!


#2

Looked at this hydrophone?

http://www.submarineboat.com/hydrophone.htm

I was thinking either more piezos to make lower impedance or a impedance matching transformer/preamp (like for an acoustic guitar) for better frequency response, but I think they cover that in later builds. The mechanics for making it waterproof were what I was looking for. Lots of interesting information on his site!

http://www.submarineboat.com/hydrophone.htm


#3

regarding enclosures you get started with the battery tube + endcaps. Gives us approx. 1 1/8” inside diameter. Without the batteries in, the tube would flex or collapse under pressure. You could go with a short tube or add plugs (or actual batteries for power) for structural support.

Another simple approach would be to sandwich together (with maybe 5 to 6 brass bolts) a couple of acrylic disks (like the endcaps) with a center section with an o-ring sealed thicker disk (would 3/8” be enough to fit electronics?), that has it’s center cut out (smaller diameter circle) like a donut. The cut out section would be large enough for the electronics and batteries. Wires would be run through a potted hole and the transducer would be mounted at the center outside surface.

A friend of mine built a simple hydrophone using a piezo disk this way. https://ccrma.stanford.edu/~sleitman/Hydrophone/

I have the unit if you want to give it a try (use from the surface only with amp - like a radio-shack mono amp)

I would like to do an enhanced version of the hydrophone as an add on to the ROV for listening to ocean/marine animal sounds. Would have to sample and stream audio to the surface.
With FET pre-amp like this:
http://makezine.com/2011/12/20/collins-lab-diy-contact-mic/


#4

YES Jim! This would be a good starting point for me to get started with experiments and possibly reverse engineer something that will work well with our beaglebones…THANKS!


#5

I just used this basic hydrophone and a Radio Shack mini AMP to receive my first test tones from a potted 40KHz piezo-ceramic transducer and the wideband power amp that we have been designing - see other blog for details

Jim


Suggestions for a DIY hydrophone?
#6

Link to other blog - http://openrov.com/profiles/blogs/acoustic-modems-location-and-pingers