This paper follows from an earlier experiment investigation1 on the sound reduction of single skin, trapezoidal profiled cladding systems, paying particular attention to the pronounced “dips” in the SRI at mid frequencies. Theoretical predictions were made to confirm the previous experimental findings. Finite element analysis was used to examine the vibration modes of the profiled cladding. The boundary element method was used to investigate the radiation efficiency of the vibration modes and their excitation by acoustic plane waves. Good agreement with measured vibration data was found. An analytical method for predicting the sound reduction index of single skin profiled cladding systems is proposed and is shown to compare well with measurements on all 15 cladding systems used in the experiment work. An empirical prediction model is also compared.

The sound reduction of single-skin trapezoidal profiled metal cladding systems often displays pronounced "dips" in mid frequency range. Because of their magnitude and frequency range. these "dips" can be a critical limiting factor in a cladding system's performance towards insulating noise from industrial premises. This paper investigates in detail the sound reduction of these cladding systems. A series of sound reduction measurements employing a systematic and comprehensive change of profile geometry involving 15 cladding systems was conducted to examine the effect of the profile geometry on the sound reduction "dips". It is suggested that the "dips" are caused by resonant vibration modes that are local to the geometry of a profile corrugation. Vibration measurements on cladding sheets excited by a diffuse field in a transmission suite and on free hanging cladding sheets excited by a normal incidence plane wave in an anechoic chamber were conducted to test and confirm the explanation.