Assembled with sensors aimed at detecting acoustic signals, and vibrations in general, in water, towed arrays are designed in order to minimize unwanted hydrodinamic noise.

Towed hydrophone are usually made of more than one sensor, in order to receive information about the direction from where a signal arrives.
Two main techniques are used to get this information: beamforming and time delay measure.

While beamforming requires high processing capabilities and excellent results (and this usually means BIG computers and quite a lot of money), time delay measure is a rather simple but less effective technique, requiring a simple PC and suitable software.

We have archived on these pages many images and ideas about arrays we have designed and/or assembled in the past years. Hope they may be of some help if you are thinking about towed hydrophones for Marine Mammal research.

Codenamed G2, this was the less expensive towed hydrophone we have ever assembled.
Maintenance was a pain in the neck, and finally we decided to cancel this product.
After quite a long period of "tuning" with the customer, who required to change the wideband sensors with narrower band (and lower noise) ones, the worst problems came from the cable.

Lessons learnt: if you can not afford a good cable, but require durability, it could be better to give up your project and change plans.

Codenamed PROTONE (PROTotype ONE), this is our test towed hydrophone.
Do not even remember how many times we have changed the sensors on this.
It is still working and in-line.
It currently has four sensors, and can be equipped with up to eight. One pressure gauge, and a nice modification to accomodate a temperature transmitter.

Lessons learnt: on a protoype you will need more wires than how you have.

Codenamed G4 (generation four), is our standard commercial towed hydrophone in 2004.
Originally re-designed for a big NGO, this is our standard product at the time of writing. Analog part going from about 100Hz to 60kHz and then again from 100kHz to 230kHz, and a digital acquisition interface, with filters, going from 0Hz to 48kHz, offers an high frequency output, for click detectors.
It is packed with software, and is worth the money !

Lessons learnt: Let's use a polyurethan hose, and provide training.

New

To fulfill many enquiries we have received, we are prototyping a "single element" towable hydrophone.
Assembled with a 50kHz sensor and low noise preamp electronics, using a long (more than 150 meters) balanced and reinforced signal transmission line (to guarantee reasonable immunity to electric noise), with a simplified amplifier and filter unit.

This system is aimed at helping "low-budget" researchers willing to get an underwater acoustic snapshot of the study area, operating from slowly moving sailing boats or from fixed coastal stations up to 500 meters from the listening point.
This hydrophone, codenamed FAR-ONE, will be branded by Nauta-rcs and will be available for tests in mid 2006.

If you are interested in receiving more information about this equipment, and ask for a demo period with it in your hands, please write.

write for infos: info@nauta-rcs.it