Directional transducers
Gerhard Martin Sessler, James Edward West · IEEE Transactions on Audio and Electroacoustics · 1971
Directional electroacoustic transducers for the audio-frequency range, based on the electrostatic principle using foil electrets, have been designed. The directivity is achieved by utilizing first, second, and higher order gradients with bidirectional, unidirectional, and toroidal characteristics. Experimental results on directional characteristics directivity factor, and frequency response for each type of transducer are described. Possible application of such directional microphones in two-way communication systems is also discussed.