Condenser Microphones with Electret Foil
A new kind of condenser microphone which utilizes a foil electret and therefore requires no external dc bias is described in this paper. The frequency response of the microphone is within ±3 db from 50 to 15000 cps. Sensitivities as high as -50 dbv re 1 µbar have been achieved. Due to its relatively low impedance, the microphone can be connected directly to conventional transistors amplifiers. Measurements over a period of about one year have shown no degradation of microphone sensitivities and indicate excellent stability of these systems.
This paper costs $20 for non-members, $5 for AES members and is free for E-Library subscribers.