Microphones utilize different electroacoustical principles to convert sound energy to electrical energy:
1. Carbon Microphone A microphone using a flexible diaphragm which moves in response to sound waves and applies a varying pressure to a container filled with carbon granules, causing the resistance of the microphone to vary correspondingly
2. Piezoelectric microphone A microphone in which deformation of a piezoelectric bar by the action of sound waves generates an output voltage between the faces of the bar. Also known as "crystal microphone".
3. Magnetic microphone A microphone employing a diaphragm acted upon by sound waves and connected to an armature which varies the reluctance in a magnetic field surrounded by a coil. Applications include miniature microphones for hearing aids and guitar pickups.
4. Dynamic microphone A conductor (coil attached to diaphragm, ribbon) flexibly suspended in the field of a fixed magnet is vibrated by sound waves. This induces in the conductor an AC voltage that varies in step with the sound waves.
5. Electrostatic microphone A flexible diaphragm and a fixed electrode together form a two-plate air capacitor whose capacitance varies in step with the sound waves that vibrate the diaphragm. Also known as "capacitor microphone" or "condenser microphone". In electret microphones one of the electrodes carries a permanent charge. |