The acoustic output produced by a steady airflow through a corrugated duct

Abstract This paper is concerned with the noise produced when there is a steady flow of air down a duct which is internally corrugated. Thus it is of relevance to situations such as heat exchanger tube bundles, dissipation-type silencers and the open undercarriage holds of an aircraft. Of particular interest here is a commercial application where low velocity air travelling along a flexible corrugated duct (of the configuration used on vacuum cleaners) can result in acoustic outputs at the duct outlet in the region of 140 dB. Experiments are described in which the phenomenon was investigated, and several methods of attenuation are discussed.