Active reduction of the two-way diffraction from a noise barrier by using feedforward control

This paper develops a feedforward (FF) structure based active noise control (ANC) system that reduces the two-way diffraction from an office partition with the aim of actively creating isolated acoustic domains in open-plan offices. The FF-ANC system can only reduce the noise downstream of the reference sensor due to the causality requirement. Therefore, a coupled FF control structure is proposed to realize the reduction of two-way diffraction. This system applies a two-source loudspeaker array as the control source, and two microphones as the reference and error sensors. The directivity of the loudspeaker array is controlled to emit the control sound only into the corresponding control area. In comparison with the preceding active diffraction reducing systems, using a directivity controlled loudspeaker array can generate an absorptive acoustic boundary rather than a reflective boundary on the diffracting edge, which can isolate the acoustic environment without adding reverberation in a room. The effectiveness of the proposed system is verified by computer simulations.