Endfire Acoustic Radiation Reduction Technique for the HF MMPP

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Authors
  1. Fleming, R.A.G.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN)
Abstract
The multi-mode pipe projector (MMPP) is a recently patented sonar projector capable of very wide bandwidth. The projector generates this bandwidth with an optimized approach to overlapping numerous drive motor and waveguide resonances. The high frequency MMPP (HF MMPP) was developed to operate over the 10-100 kHz band with a broadside transmitting voltage response of greater than 122 dB re 1μPa/Vrms @ 1m. This projector has recently been employed as a communications source over the 35-50 kHz band in the Networked Autonomous Littoral Surveillance (NetALS) program. The NetALS application involves orienting the HF MMPP vertically near the ocean bottom and using its horizontally-omnidirectional broadside acoustic radiation. However, since the endfire acoustic radiation of HF MMPP can be as much as 12 dB greater than the broadside acoustic radiation, there is increased likelihood of multipath distortion from endfire-generated surface and bottom reflections. A technique has been developed for diminishing endfire acoustic radiation which requires mounting a rigid air-cavity at a specific distance from each of the HF MMPP’s endcaps. A prototype of the air-cavity attenuation technique reduced endfire TVR by more than 10 dB over the 35-50 kHz band.

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Report Number
DRDC-ATLANTIC-TM-2006-261 — Technical Memorandum
Date of publication
01 Nov 2006
Number of Pages
30
DSTKIM No
CA029038
CANDIS No
527290
Format(s):
CD ROM

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