Electret Microphones: Components, Mechanism, and Types

Electret microphones are a type of electrostatic capacitor-based microphone that eliminates the need for a polarizing power supply. They contain a permanently charged material known as an electret, which allows them to function without external power. This type of microphone has a built-in charge that produces a small electrical output, requiring an operational amplifier circuit for signal amplification. The electret material used in these microphones has very high resistivity and stability, ensuring longevity. Different types of electret microphones include foil-type, back electret, and front electret, each serving specific purposes in sound capture and reproduction. Understanding the components, mechanism, and types of electret microphones is essential for audio recording and sound engineering applications.

• Electret Microphones
• Components
• Mechanism
• Types
• Audio Recording

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1. Electret Microphone Group 2 Michael Ruscito Jinghan Huang Mingshi Yang Tomas Pavydis

2. What is it? A type of electrostatic capacitor-based microphone, which eliminates the need for a polarizing power supply by using a permanently charged material. An electret is a stable dielectric material which contains a permanent electric dipole charge Electrets are created by melting dielectric materials which contain polar molecules and allowing the material to re-solidify in a strong electrostatic field

3. Components Permanent built-in charge in parallel with a conductive metal backplate (does not need power to operate) Only produces a very tiny electrical output, so requires an Operational Amplifier circuit to amplify its signal. (This requires power)

4. About the built-in charge Material has very high resistivity. Made by heating and form dielectric material in strong electric field. Due to the high resistance and chemical stability of the material, will not decay for hundreds of years

5. Mechanism Similar to all condenser microphones, the built-in charge is pushed closer or further apart from the backplate by pressure of sound wave. The vibration generates a small ac voltage proportional to the sound pressure, which serves as the output signal. The output signal can be converted to sound by connecting it to an audio device such as a speaker

6. Types of Electret Microphones Foil-type or Diaphragm-type - A film of electret material is used as the diaphragm itself. This is the most common type, but also the lowest quality, since the electret material does not make a particularly good diaphragm. Back electret - An electret film is applied to the back plate of the microphone capsule and the diaphragm is made of an uncharged material. Front electret - Newest type, the capacitor is formed by the diaphragm and the inside surface of the capsule. The electret film is adhered to the inside front cover and the metalized diaphragm is connected to the input of the FET. It is equivalent to the back electret in that any conductive film may be used for the diaphragm.

7. References What Is an Electret Microphone? What Is an Electret Microphone?, LearningaboutElectronics, www.learningaboutelectronics.com/Articles/Electret-microphones. Condenser Microphones Condenser Microphones , LearningaboutElectronics, http://www.learningaboutelectronics.com/Articles/Condenser-microphones Moeller, and Paul. Electret Condenser Microphone (ECM). Institut F r Nachrichtentechnik Technische Universit t Darmstadt, www.nt.tu- darmstadt.de/startseite_nt/fachgebiete_nt/ehemalige_fachgebiete_nt/fachgebiet_elektroakustik/glossar_1/elektretmikrofo n_nt_ea/ecm_ea_nt_1.en.jsp. Notes, Electronics. Electret Microphone. Electronics Notes, www.electronics-notes.com/articles/audio- video/microphones/electret-microphone.php.

8. Thank You