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RE: [PSUBS-MAILIST] Sound contact ! ( Dolphinear hydrophones )



Peter,

If I understood correctly, you suspended the cable in "mid air" from the sensor to the control room to negate mechanical contact (rubbing).

If so, It will be interesting to see what a permanent installation will look like, what kind of insulating material is used.

This is good news.....and yes...sounds like fun!

Joe


From: "Peter Madsen" <peter@submarines.dk>
Reply-To: personal_submersibles@psubs.org
To: "support" <support@doyle-renney.com>
CC: <personal_submersibles@psubs.org>
Subject: [PSUBS-MAILIST] Sound contact ! ( Dolphinear hydrophones )
Date: Wed, 23 May 2007 01:08:03 +0200

Ken,

I asked a scientist at the Technical University of Denmark who is a friend of mine to take a closer look at your hydrophone - and I received my self #2 hydrophone.

During a test over the side of a boat It did exactly the same as the first - ergo - no ( likely ) error in the amplifier or hydrophone.
Then tonight - my scientist called me with his conclusions:

Result 1: I know to little of how to use highly sensitive instrumentation like this.

Result 2: Given instructions on how to install and use the hydrophone - it turned out to be a very usefull sensor - especially in combination with a submarine.

My friend concluded the DolphinEar is a good and very sesitive hydrophone at its cost - yet he recommended a better cable, or the amplifier to be build into the hydrophone itself.

He explained that the cable must be handled with extreme care not to produce noise, since it itself has a pieco electric effect - hence makes noise when
mechanically stimulated.

He also explained that the polymer and epoxy parts would not have unlimited life in a marine environment. This is not a problem for the DolphinEars normal use but when installed permanently submerged on the sub it would become a problem over time. Polymers simply are not impenetrable by water.

Tonight the first hydrophone was therefore installed like this...in Kraka´s bow we have two flat acrylic viewports. The sensor was placed on the INSIDE of the one viewport, and in very intimate contact with it. The cable was pulled back to the controlroom and secured so that its not mechanically disturbed.

Then our black u-boat sailed into the indeed very black harbor and submerged. The boat leveled out at 18 foot of water and the device was turned on...WOILA...very low noise...I can hear any sound generated in the boat - a relay clicking - if I scratch the paint - the sound of a minute HP air leakin the sea outside...any sound in the boat is heard very magnified. At this point a challup form our Royal Yacht "Dannebrog" - moored at in the harbor started its propeller - and Kraka´s new listening gear immediately detected the sound contact...long before I could hear it the "normal" way. Once it got so close I could hear it directly - the hydrophone was overwhelmed and made the noise I have complained about.

Conclusion:

DolphinEar hydrophone are useful in submarines - but must be installed with care. They are exceptionally sensitive to solid and liquid transferred sound - and this was mis interpreted by me.

We now have to find out how its directional characteristic is in this mounting - or perhaps improve it. Initially I will place the other hydrophone in the starboard window and see what that does to us... In my opnion - there is a lot more to be learned and lot more potential for these hydrophones in combination with underwater recreational vessels. The sound dive was really fun.

Best regards,

Peter Madsen / Submarines.Dk

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