Reduction of Noise Transmission in a Duct by Termination Impedance Control of a Sidebranch Resonator

Abstract

This paper investigates the use of a sidebranch resonator subjected to active termination impedance control as a means to reduce noise transmission in a duct. The main purpose of this paper is to establish a method for controlling a broad-band noise, which is characterized by a simultaneous incidence of a large number of frequency components. To this end, a control law is expressed in terms of a controller transfer function, and a new method for accurately implementing the desired frequency characteristic of the controller transfer function over a wide frequency range is presented. In this method, the inverse Laplace transform of the controller transfer function is expressed in terms of a Fourier series. This expression leads to an online computation algorithm that allows us to update the values of base functions of the control force at each digital sampling time. The effectiveness of the algorithm is demonstrated by computer simulation.