Adaptive-passive quarter-wave tube resonator silencer

Abstract

An adaptive-passive quarter-wave tube resonator silencer was experimentally tested using recorded in-duct recipro-cating engine exhaust noise. The exhaust noise was re-played through a loudspeaker attached to one end of a duct, and the adaptive passive system was able to track changes in engine speed and provide attenuation of the noise at the fundamental firing frequency of the engine and the third harmonic. The control system used a novel method of de-termining the phase angle of the transfer function between the pressure in the quarter wave tube and the main duct by using a sliding-Goertzel algorithm to calculate the Fourier coefficients.