Characteristic to the electret transducer in accordance with the invention is the fact that between the electret material (1) and the surface layer (3) material layer (2) transversally conducting electricity has been placed.

The microphone can be carbon, electret or dynamic.

This invention relates to an electret material having thermal stability and capable of having high trapped charge quantity and stably existing for a long period of time and a process for preparing said electret material.

Electret fibers that contain a polymeric material and a fluorochemical additive.

The second electrode structure is arranged on or above the electret material, with the result that the electret material is situated between the first and second electrode structures.

An electret microphone (20) is located in the chamber (18).

A filter that includes a first electret filter layer through which an airstream first passes before encountering a second electret filter layer.

Disclosed is an electret which comprises a first region and a second region.

The peel pouch may be electret treated prior to insertion of the article to be sterilized.

Alternatively, an electret can be deposited on the surface of the semiconductor.

The filter media is useful in electret filters when charged.

Both the electret dielectric (3) and the electrodes (5a, 5b) are flexible.

The present invention provides a self-supporting laminate filter medium having an electret lofty spunbond web and an electret microfiber web, wherein the spunbond web has a density between about 0.01 g/cm3 and about 0.1 g/cm3.

Methods of making and using patterned electret fibrous webs are also disclosed.

A miniature electret microphone includes an input buffer circuit.