Second order toroidal microphone
US4675906A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 20, 1984 |
| Grant date | Jun 23, 1987 |
| Priority date | — |
| Expiry date | Dec 20, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04R1/406
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.