An active noise control device or an active noise absorber (ANA) that is based on either resonant 2nd - order or 4th - order Butterworth filters is developed and demonstrated. This control method is similar to structural positive position feedback (PPF) control, with two exceptions: 1) acoustic transducers (microphone and speaker) can not be truly colocated, and 2) the acoustic actuator (loudspeaker) has significant dynamics that can affect performance and stability. Acoustic modal control approaches are typically not sought, however, there are a number of applications where controlling a few room modes is adequate. A model of a duct with speakers at each end is developed and used to demonstrate the control method, including the impact of the speaker dynamics. An all-pass filter is used to provide phase compensation and improve controller performance. Two companion experimental studies validated the simulation results. A single mode case using a resonant band-pass filter demonstrated nearly 10 dB of control in the first duct, while a multimodal case using two 4th - order Butterworth band-pass filters show both 10 dB of reduction in the fundamental mode and nearly 8.0 dB in the second.
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