Investigation of the Poor Mid-Frequency Sound Reduction Characteristics of Profiled Cladding

Pro led metal cladding constructions are an Increasingly prevalent feature of modem industrial architecture.Whilst such materials conform to high sthcturai standards.their acoustic Characteristics are often poor.Previous work by the authors [1] has shown tint large depressions In the single-skin sound reduction (of up , to tOdB In magnitude) occur at mldband frequencies and are most likely caused by certain vibrational modes.When the profiles are incorporated into more common double leaf structures.the dip in transmission loss remains These features have also been noted during In sltu measurements [2]. it Is considered that this potemiaily posesa significant environmental noise problem.Present methods of predicting transmission through cladding tel because they are global approaches.to they are unable to accoum for "Iocallsed effects such as speci c vibratioml modes For example.Hecki s method [3] Is known to provide a reasonable estimation [2].but will be Inaccurate where the described dips occur.Consequently.this paper shall attempt to establish exactly the physical process which precipitates the dips In sound reduction.In order