Noise levels at the Mulwala plant of Australian Defence Industries (ADI) were reviewed by Marshall Day Acoustics as part of an overall environmental review conducted by the company.Progressive surveys were conducted at various process facilities, including the TNT, RDX and other chemicals' facilities used in the organisation. The survey indicated that the variable nature of production resulted in different noise levels in the nearby community at different times of the year. Some plants operated for only a few weeks, whereas other plants operated for months at a time.

The overall impact was such that noise limits required by the NSW EPA were found to be in excess along one boundary of the plant, in the vicinity of a local housing estate.Marshall Day Acoustics carried out a noise impact analysis and reviewed the costs associated with achieving compliance with the EPA requirements. The major noise source was found to be the boiler house, located immediately on the boundary and only 60m from the nearby houses. Practical noise measures, such as acoustic enclosures and burner fan silencers, were required to achieve the project noise limits. In spite of its remote location on over 1,000ha of land, the unfortunate juxtaposition of some parts of the process facility and the nearby residents resulted in the community noise problem. ADI is taking remedial action to rectify the problems to ensure that the noise limits set by the NSW EPA are complied with.