On the “In-Situ” Control of Acoustic Liner Attenuation Available to Purchase

In this paper a concept is presented which enables the attenuation of sound in a lined duct to be controlled via the control of the fundamental liner characteristic (the acoustic impedance). The concept is described and modeled by a semiempirical analysis. The feasibility is demonstrated by means of measurements of attenuation and local impedance in a small scale flow duct test facility.