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Jim, The military used hydrophones formed in a circle. Since sound propogates from a single point of origin, it expands from this point in an ever enlarging circle. These sound waves would eventually encounter this hydrophone array and strike specific hydrophones in a set given order as it continues to pass thru this array. The military having almost endless resources had the ability to determine the bearing to the point of this sounds origin by this sequence of detections and hence where it came from. Dealing with Psubs, we have limited space, limited funds, and the need for exact contact bearing of detection is not critical. I too am at a loss as to the lack of bearing accuracy now being shown from these later units. The initial "dolphin ear" hydrophone had almost no side detection capability and the level of detection increased as the source became closer to ninty degrees from the piezo elements mounting surface. It was bi-dirrection as back side detections were also part of its beam pattern. I need to go back and redesign this unit so as to regain its dirrectionality (Is there such a word?) Where is your location, and do you feel like participating in this road of discovery? Your input, testing, and evaluations would be a great asset to us all. Do you have a working sub or one under construction? Are there lakes, ponds, or other bodies of water nearby for testing? David Bartsch From: kocpnt@tds.net To: personal_submersibles@psubs.org Subject: Re: [PSUBS-MAILIST] Convention Date: Mon, 4 Aug 2008 21:02:13 -0500 Hi David,
I think that the underwater hydrophone testing went well. The results were not as good as hoped for from a directional standpoint. I brought up that if we used some of the same components and made the tube from steel or some othe dense material, I think that directionality will be improved. This is just a guess. Perhaps the opposite is also true, you could use the similar tube and some insulation to soften the reaction of the outside diameter of the tube and allow the acrylic front take a higher percentage of the feedback. I feel as if one or the other of these approaches are worth testing for positive directional results.
Best Regards,
Jim K
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