1 Electret microphones use a polarised condenser instead of a crystal.

2 Polypropylene electret shows good curative effect for chilblain, arthritis and furuncle.

3 Electret air filter material has superior filter performance, as ideal filter material for coal - dust stained yarn.

4 The ASTATIC 901 is a superior low noise, electret condenser cardioid surface mounted boundary microphone.

5 It'specilizes in manufacture of carious circle receiver, electret receiver and accessories of various telecommunication product.

6 The melt blown nonwoven technology, the electret theory and electret nonwoven are introduced in this paper.

7 Electret air filter material has superior filter performance, so it is considered as ideal filter material for coal-dust stained yarn.

8 The principle of electret condenser microphone and its noise are analyzed in the paper. It will be helpful to improve the electric specification.

9 The electret microphone tester is used to test electret microphone's sensitivity and frequency response.

10 Experimental results point out that the said copolymer electret film is a polar material, i. e. there exist both oriented dipoles and deposited space charges in the film after charging.

11 The rule of the shift of the mean charge depth at different environmental humidity was discussed for this electret material by heat pulse method.

12 It also gives a safety design problem analysis using an electret capacitor microphone to pick-up the heart sound signals.

13 Theoretical evaluation and simulation experiments show that the improved BP neural network can effectively detect the image feature of electret condenser microphone.

14 SD rats were divided into 3 groups: control, scald and electret group.