The Author, of the Becker-Akustik Company, Sweden, discusses the reduction of structure-borne noise from ships' machinery, and points out that if the noise could be reduced by applying visco-elastic material to the strucure, so increasing the loss factor, this would be a very attractive solution. A good knowledge of the noise propagation process is necessary for the success of the method. Experiments conducted on the application of visco-elastic materials in ships in service have shown that significant noise-reduction can be achieved. An account is given of a case in which noise from a ballast pump, mounted alongside the engine in a 1,250-dwt motor-ship and stiffly connected to the hull structure at several points, badly affected the spaces above the pump. To treat all possible noise-transmission paths, visco-elastic material was applied to all plating around the pump and its piping. A free layer, 15 mm thick, of a two-component damping compound was applied to the tank top; elsewhere, a constrained-layer (sandwich) technique, e.g. a 5-mm layer of Beckler-Akustik TK 301-7002 compound covered by 0.8-mm steel sheet, upon 10-mm shell plating, was used. The results of this treatment are shown in graphs and discussed; in an officers' mess above the pump, the noise level from the pump was reduced by 10 dB(A), and there was also a reduction of 6 dB(A) in the structure-borne noise from the main engine. The article includes some general practical advice on noise-reduction treatment with visco-elastic compound in existing ships, and mentions that after some development it may be used (together with other methods) in new ships. A good method, in new ships, would be to employ the constrained layer technique, and the cost of this could be reduced by using, for example, sprayed concrete instead of steel sheet; curves from laboratory measurements of loss factor are given for combination of 10-12 mm concrete and 1-2 mm compound (TK 301-7002) applied to 10-mm steel plate. Order from: BSRA as No. 47,674.

  • Corporate Authors:

    Trade and Technical Press, Limited

    Crown House
    Morden, Surrey SM4 5EW,   England 
  • Authors:
    • Aztely, J
  • Publication Date: 1977-10

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Filing Info

  • Accession Number: 00173715
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 26 1978 12:00AM