Investigation of Decoupling Material Performance with a Transmission Loss Model and Acoustic Intensity Measurements

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Authors
  1. Klein, K.
  2. Liu, Q.
  3. Guigne, J.Y.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN);Guigne International Ltd, Paradise NFLD (CAN)
Abstract
The complex dilatational moduli of three closed cell foam materials and one elastomeric material were determined by mechanical excitation of thin samples. The neoprene/EPT/SBR, polyvinylchloride, and ethylvinylacetate foams had moduli that ranged from 0.2 MPa to 3 MPa in the 100 - 900 Hz frequency range. The decoupling performance of these materials was then determined by applying them to steel substrates that were mechanically excited, and measuring the effect of the coatings on the radiated sound. Unlike previous studies where the test plates were suppored at the corners and semi-submerged, in this study the plates were clamped at the edges and backed by an air filled concrete enclosure. This "concrete box" was submerged into a water filled tank and the radiated sound was determined by intensity mapping in the near field of the plate. Because the net radiated acoustic power was not uniformly positive across the frequency range studied (100 -900 Hz), a quantity related to the near field acoustic power sum (I)dA, was used to quantify the effect of the coating. The experimental decoupling behaviour of the coatings was compared to that predicted by a one dimensional transmission loss model for the 4 layer system: air/steel/coating/water; or for the 5 layer system that included the finite dimensions of the water layer in the tank: air/steel/coating/water/air. TRUNCATED
Keywords
Decoupling;Vibro-acoustics;Closed cell foam coatings;Acoustic radiation;Radiated noise
Report Number
DREA-CR-1999-127 — Contractor Report
Date of publication
01 Sep 1999
Number of Pages
137
DSTKIM No
CA001524
CANDIS No
513477
Format(s):
Hardcopy;Document Image stored on Optical Disk

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