An impedance-based control system and its application to active noise control

The active noise control system of analogue using impedance is analyzed to test its feasibility and the realization method is proposed. This type of system has several advantages compared with conventional microphone-loudspeaker type system because no microphone is required in the system. In this paper, a bridge circuit is used to measure and control impedance. The output of the bridge circuit is analyzed in two categories: Active Sound Restrain and Active Sound Absorption. In addition, the relation is discussed between the output of the bridge circuit and the input of primary source. Although some experimental results are not satisfactory because of the low efficiency of the electro-acoustic transducer, the new method of active noise control based on source impedance is proved feasible and can be used into practice.