Pressure gradient electret microphone
US4258235A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 3, 1978 |
| Grant date | Mar 24, 1981 |
| Priority date | — |
| Expiry date | Nov 3, 1998 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04R19/04
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A pressure gradient electret microphone provided with a plurality of channels extending between ports located in a ring of plastic material disposed about the periphery of a cylindrical back plate. Each of the channels expanding in horn fashion from the port at the diaphragm chamber to ports in the casing, and the ports in the casing being provided with an electrically conducting shield connected to the electrically conducting casing. In one embodiment of the invention, a line extends from the forward side of the diaphragm, and the line is provided with an aperture adjacent to the diaphragm coupling the diaphragm to the surrounding sound field at frequencies below the critical frequency of the line.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.