Patent ID: 7492910

Claim:
A system for actively treating noise within a fluid-carrying duct comprising: a fluid-carrying duct; a source of acoustical disturbance within the fluid-carrying duct, wherein the acoustical disturbance defines at least one frequency of disturbance within the fluid-carrying duct; an acoustic wave sensor positioned to sense fluid pressure within the duct, wherein the acoustic wave sensor is operative to produce a first signal representative of the frequency of disturbance; an acoustic wave actuator positioned to manipulate fluid within the duct, wherein the acoustic wave actuator is substantially collocated with the acoustic wave sensor; and an electronic feedback controller defining an input coupled to the first signal and an output coupled to the acoustic wave actuator, wherein the electronic feedback controller generates a second signal at the output by applying a feedback controller transfer function to the first signal, the feedback controller transfer function comprises a transfer function that operates with the acoustic wave actuator to simulate a low pass acoustic filter comprising a transfer function of the form LP=Cs 2 where C represents compliance of the simulated low pass acoustic filter and s is the Laplace variable, a high pass acoustic filter comprising a transfer function of the form HP=1/L, where L represents inertance of the simulated high pass acoustic filter, or a band-reject acoustic filter comprising a second order differential equation transfer function comprising a first variable representing a predetermined damping ratio and a second variable representing a tuned natural frequency.