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Electret Microphones

Electret Microphones. Michael Chakinis, Brianna Undzis, Swan Htun, Barrett Neath. How Regular Microphones Work. Sound propagates through air in the form of waves A thin, flexible diaphragm is contacted by waves Moving diaphragm creates varying current Dynamic Induction Condenser

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Electret Microphones

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  1. Electret Microphones Michael Chakinis, Brianna Undzis, Swan Htun, Barrett Neath

  2. How Regular Microphones Work • Sound propagates through air in the form of waves • A thin, flexible diaphragm is contacted by waves • Moving diaphragm creates varying current • Dynamic • Induction • Condenser • Capacitance • Ribbon • Induction • Crystal • Piezoelectricity effect

  3. How the Electret Microphone Works • The electret condenser microphone works on the principle of variable capacitance • Use a parallel plate capacitor with a fixed and moveable plate • When sound waves hit the moveable plate, it changes the capacitance and electric flow • They’re made by melting a dielectric material then solidifying it to a strong electrostatic field • Being chemically stable and having high resistance embeds a permanent electric dipole moment • It can be connected to a JFET (Junction Field Effect Transistor) to increase the generated electric current

  4. Different Types of Electret Microphones • There are three main types of electret microphones: front electret, back electret, and foil-type. • Front Electret • Newer • Back plate eliminated • Capacitor formed by diaphragm and inside surface of capsule • Electret, inside front cover • Any conductive film may be used for diaphragm • Back Electret • Electret film applied to back plate of microphone capsule • Diaphragm, uncharged materials • Transducer design • Physical quantity -> electrical signal • Foil-Type • Film of electret used for diaphragm • Most common • Lowest quality

  5. Relevant Equations • Variations in air pressure is detected by the diaphragm. • The voltage change is induced by the varying distance between the diaphragm and the back plate due to voltage fluctuations across the capacitor. • Thus, across the the diaphragm and the back plates, the voltage varies accordingly with the vibrations in the air given by the capacitance equation: • C = Q/V

  6. Sources https://en.wikipedia.org/wiki/Electret_microphone https://www.mediacollege.com/audio/microphones/how-microphones-work.html https://www.engineersgarage.com/insight/how-electret-condenser-microphone-works http://hades.mech.northwestern.edu/index.php/Microphones https://www.cui.com/product-spotlight/electret-condenser-microphones

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