An Electret Loudspeaker for Active Acoustic Systems

Abstract

A push-pull electret loudspeaker has been developed which can be used for an active acoustic wall lining.

Active Impedance Control for One-Dimensional Sound

“…Similar results have been obtained with a specially developed electret loudspeaker [8] instead of the moving-coil system. In order to get a reflection coefficient below 0.2 in the same frequency range as above, a third-order all pass filter appeared to be necessary.…”

Active Reflectors for Room Acoustics

“…each composed of a sensor (microphone), an electronic control circuit, and an actuator (loudspeaker) situated close to the associated sensor. Guicking [3] and Hen [4] have proposed digital filters that can cancel the direct path from the loudspeaker to the associated sensor, but they could not realise an array of such cells (cost, cell interaction). Ideally, the aim is to control the acoustic impedance of the wall ; therefore this topic is often referred to as active impedance control.…”

On the significance of reflection coefficients produced by active surfaces bounding one-dimensional sound fields

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] In contrast to elements of artificial reverberation systems, which attempt to recreate or synthesize desired acoustical signatures in rooms, these elements are intended to directly alter acoustical properties of enclosure boundaries or interact with primary sound sources to control specific sound field quantities.…”