Active acoustic impedance control system for noise reduction

摘要

The device operates actively to reduce low frequency noises.- DETAILED DESCRIPTION - The device provides active control of the acoustic impedance in an audio transducer (1) within the medium to which the transducer radiates. The system comprises at least one impedance bridge, on branch of which includes an electrical impedance between the transducer terminals. The circuit includes provision for measuring the transducer membrane velocity, and for measuring the acoustic pressure exerted on the transducer membrane. Pressure measuring is achieved by means of sampling a measuring voltage (Vd) on the impedance bridge. The excitation voltage (VR) applied to the impedance bridge (2) is a combination of two measured values