MEASUREMENTS OF SOUND INTENSITY AS A TOOL FOR COMPARING THE RELATIVE MERIT OF NOISE REDUCTION COATINGS

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Authors
  1. Klein, K.
  2. Hamm, C.A.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN);Guigne International Ltd, Paradise NFLD (CAN)
Abstract
Underwater measurements of acoustic intensity were used to examine the radiated acoustic field from semi-submerged coated steel plates in both free field and enclosed tank conditoins. The objective was to investigate acoustic intensity based methods of assessing the capability of hull coatings to suppress radiated sound. Measurements occurred in the 100 to 800 Hz frequency range. EAR and closed cell foam coatings were tested on 9.5 x 604 x 604 mm steel plates. Bare plates were also tested for comparison. Two performance indicators based on measured acoustic intensity were developed for comparing coatings and used to examine the data. Acoustic intensity measurements were found to be a very useful diagnostic tool for this application. The measurements were used to examine net radiated sound power and also the amount of power circulating in the acoustic near field. Examination and comparison of the resulting data brought several unsuspected weaknesses in the test process to light. The base steel test plate (i.e. the test platform) needed to be a strong acoustic radiator to facilitate measuring the reduction in radiated power due to the addition of a coating. But the net radiated power calculated from the acoustic intensity measurements identified that the test platform was, in fact, a weak acoustic radiator. This characteristic made the test process more vulnerable to error. TRUNCATED
Keywords
Acoustic intensity;Decoupling;EAR coatings;Closed cell foam coatings;Acoustic radiation
Report Number
DREA-CR-97-442 — Contractor Report
Date of publication
01 Sep 1997
Number of Pages
81
DSTKIM No
98-00600
CANDIS No
507351
Format(s):
Hardcopy;Document Image stored on Optical Disk

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