Control of Noise Sources on Sea-Going Tow Boats

Abstract

The paper describes noise-control studies on a number of commercial tow-boats operating on the North-Pacific coast. Noise levels in these small vessels often exceed 80 dBA in the sleeping accommodation areas. Crew may be continuously exposed to these high levels of noise for periods of several days. A variety of diagnostic techniques have facilitated the separation and localization of sources of structure-borne and air-borne sound. These include the use of artificial sources, spectral and cross-correlation analysis, vibration analysis, and statistical energy methods, together with the less sophisticated trial and elimination approach. On most boats, structure-borne vibration made the greatest contribution to noise levels in occupied spaces. The high noise levels were directly attributed to one or more mechanical deficiencies on each boat. Such deficiencies included faulty bulkhead design, inadequate acoustic isolation of crew quarters, and, principally, the widespread practice of mounting the engine, gear box, and ancillary components rigidly to the main structural elements of the vessel. Implementation of noise-control recommendations resulted in significant noise reduction on several vessels. Quantitative results for isolation of both engines and occupied spaces are presented.