Control of Noise Transmission into a Cylinder Using Adaptive Helmholtz Resonators and Passive Vibration Absorbers

Abstract

This paper describes a method for controlling broadband sound transmission into a cylinder using passive vibration absorbers and adaptive Helmholtz resonators (HR). Both frequency and time domain models of the system are developed. The control law, called the dot-product method, uses two microphone signals local to each HR, in order to tune the resonator to peaks in the spectrum by altering the neck length of the resonator. The model as well as an experiment on a large composite cylinder shows that the dot-product method can track changes in the natural frequency of a targeted acoustic mode in order maintain performance. Numerical simulations also demonstrate that the dotproduct method can tune the HRs to a near optimal solution over a broad frequency range (40-160Hz).