Predictions and measurements of the acoustical properties of clamped and perforated poroelastic plates in a duct

Results of acoustical measurements on configurations that exploit the elasticity of clamped and perforated porous plates in a flow duct are reported. The acoustic insertion losses of perforated poroelastic plates mounted transversely across a flow duct without and with flow have been measured at various locations in the duct. Results of predictions of perforated porous plate insertion losses without airflow have been found to be in reasonable agreement with data. With air flow the insertion loss caused by the lower perforation ratio is found to be approximately 3 dB higher than it is without air flow over the frequency range of the measurements. Other measurements have shown that idealized silencers made from clamped poroelastic plates mounted on the walls of a flow duct in front of an air cavity result in useful narrow band insertion losses in flow.