Miniaturized unidirectional electret microphone

摘要

An electret diaphragm is housed in a case, a back electrode is disposed opposite the back of the electret diaphragm, a damper cloth is disposed in contact with the back of the back electrode, and a terminal plate is placed behind the damper cloth and connected with the back electrode. The back electrode, the damper cloth and the terminal plate are held by a tubular back electrode holder. The back of the back electrode holder is closed by a printed circuit board to define a rear compartment in the back electrode holder, and an impedance converter is disposed in the rear compartment. A sound hole is made for intercommunication of the rear compartment with the outside to achieve unidirectional directivity.