Combined Feedback Design of Active Noise Control and Face Velocity Control Based on a Novel Secondary-Path Model of Speaker-Duct Systems

Abstract

Active noise control (ANC)-based systems provide good low-frequency noise attenuation by destructive interference between the secondary signal from an acoustic actuator (speaker) and the primary noise of the acoustic field (duct). A novel secondary-path model that described by two cascaded transfer functions and two disturbances for speaker-duct systems is first developed in this study. One disturbance is imposed on face velocity of actuator speaker that is usually ignored in ANC systems while the other is on sound pressure at a given location in the duct. The transfer functions are identified with measurements from a developed velocity sensor and a microphone, respectively. A combined design of ANC and face velocity control (FVC) based on the identified secondary-path model is further proposed to set up an adaptive feedback ANC/FVC controller with a modified filtered-X recursive least square (FXRLS) algorithm to update controller coefficients to reduce noise levels near microphone location. Results of experiments show that the adaptive feedback ANC/FVC controller has a noise reduction performance of ∼27-46dB for noise at a frequency between 100-200Hz, as compared with ∼10-35dB for that of the conventional feedback ANC design. Furthermore, the adaptive feedback controller reveals a good capability to reduce the noise level for time-varying noise of a frequency sweeping from 100 to 200Hz. Our data demonstrate a substantial improvement in the low-frequency noise attenuation using the developed controller that includes commonly overlooked factors and support the feasibility of our proposed approach in practices.