Bell Telephone Laboratories

American Telephone and Telegraph, Co.

At&t Company, At&t Bell Laboratories

Martin Sessler

James Edward West

A second order gradient microphone with unidirectional sensitivity pattern is obtained by housing each of two commerically available first order gradient microphones centrally within a baffle. The baffles have flat surfaces, are preferably square or circular and have parallel surfaces the two baffles being parallel to each other. The rotational axes of the microphones are arranged to coincide. The output signal from one of the microphones is subtracted from the delayed signal output of the other.

Unidirectional second order gradient microphone

A second order gradient microphone arrangement is implemented with four commercially available, inexpensive first order gradient electret microphones which are arranged in the wall of a hollow cylinder at ninety degrees angular spacings and whose outputs are added to produce a toroidal directional characteristic. The distance between the tops of the microphones and the top of the cylinder equals the distance between the bottoms of the microphones and the bottom of the cylinder. The directional characteristic is relatively frequency independent. The arrangement is characterized by rotational symmetry around the cylinder axis and further by a cosine squared dependence in the planes containing the rotational axis. In the direction of the axis, the sensitivity at midfrequencies is typically twenty decibels lower than in the equatorial plane. The equalized frequency response in this plane is within .+-.3 dB from 0.3 to 3 kHz.

Growing community of inventors

Darmstadt, Germany

Martin Sessler