Broadband active noise control with transfer path equalization

Abstract

Active systems for noise reduction are typically of interest for applications in which low frequency noise is a main source of disturbance and only limited amounts of installation space and payload are available. When applying active noise control methods in small aircraft cabin areas such as the crew rest compartment of a long range jet, the transfer path between sensor and actuator is strongly influenced by room acoustics and transducer behavior, thereby affecting control in a frequency selective manner, especially when using filtered reference algorithms. In this study, a concept for transfer path equalization in a feedback control approach with virtual microphones and the feedback filtered reference least mean squares algorithm are evaluated. The implementation and influence of the prediction error filter based equalizer on broadband active noise control are analyzed in simulation as well as in experiments in an acoustic mockup. The use of the equalizer improves broadband attenuation (f < 350 Hz) by 2-4 dB with a total attenuation of up to 20 dB at the error sensor. © 2011 Acoustical Society of America.