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Profesional Hydrophones can be very expensive, but this doesnt have to be the case unless your being funded by a major research grant. . Checkout DolphinEar for a reasonable Hydrophone which isnt too expensive, or why not make your own. It's a lot easier than you think.

Basically you need a waterproofed transducer fixed to a sound board, and then a pre-amplifier to increase the signal strength for listening on headphones or recording.

Obviously Whales & Dolphins produce sounds over a wide range of frequencies, not all of which can be heard by the human ear. Thats why its advisable to record as well as listen in order to manipulate the sound in your computer when you get back from your trip. Spectral analysis is an ideal way of 'seeing' the sound frequency and identifing the source.

Humans generally hear sound waves whose frequencies are between 20 and 20,000 Hz. Below 20 Hz, sounds are referred to as infrasonic, and above 20,000 Hz as ultrasonic.
We know a great deal about human hearing, but what about the hearing of large whales? Currently, we do not have detailed audiograms for the larger, baleen whales (note: we do have information on the hearing of smaller porpoises and dolphins from research with captive animals). Instead, we assume whales can hear the range of sounds they produce.

This is one way to put together a Hydrophone. It is not the best way, but the end result is pretty satisfying. And it doesn't cost much (once you have a soldering iron).

Parts list:
• Piezo Electric Transducer
•1/4" Phone Jack
• 24AWG "audio cable" 2 core wires plus shield
• Heat shrink tubing,
• An old CD disc to act as a sound board
• 2 part epoxy glue

The functional element - a piezo electric transducer is commonly used as a speaker in musical greeting cards etc, however the transducer can be bought directly from electronic stores such as Maplins, just get one with a suitable frequency range.

Clean the surfaces of the cd and the flat side of the transducer, and glue the transducer to the centre of the cd using the 2 part epox and allow to cure. (The cd acts as the soundboard)

Cut off about a 3 foot length of wire and strip the ends. Twist one of the wires together with the ground shield, and tin the ends of the wire with solder. Do this on one end only. On the other end of the cable, cut off the ground shield so that only the two insulated wires are exposed.

Unscrew the housing from a 1/4" jack. Solder the combined ground wire to the earth contact, and the 'signal' wire (white) to the centre contact point

. Tin both wires on the other end of the cable. Put two short pieces of heat-shrink tubing on the PZT leads and over the end that connects to the jackplug. Solder the two wires to the wires on the transducer. You line up the tinned wires to be soldered side by side or some people prefer to twist both ends together before tinning and soldering.

Pull the heat shrink tubing back over the solder joints. Use a hair dryer to shrink the tubing over the joints, and over the jackplug end. Water proof the back of the transducer using a thin epoxy mix and thats it, you're done. You now have a working hydrophone. Get your self a little microphone pre-amp (preferably battery operated i.e. from Maplins) and a portable set of headphones, and listen the day away. You can also record this if you have a portable recorder for analysis later.

If you want further details contact us using the contacts page.

Note: drimnin.com accepts no responsibility for making or using any form of hydrophone, if you dont think you have the skills, Buy one!

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		Drimnin.com 'Sea & Hear' Whales &Dolphins...in the Sound of Mull - West Highlands - Scotland