Principle: sound moves the cone and the attached coil of wire moves in the field of a magnet. The generator effect produces a voltage which "images" the sound pressure variation - characterized as a pressure microphone.

• Relatively cheap and rugged.
• Can be easily miniaturized.

• The uniformity of response to different frequencies does not match that of the ribbon or condenser microphones.

Principle: the air movement associated with the sound moves the metallic ribbon in the magnetic field, generating an imaging voltage between the ends of the ribbon which is proportional to the velocity of the ribbon - characterized as a "velocity" microphone.

• Adds "warmth" to the tone by accenting lows when close-miked.
• Can be used to discriminate against distant low frequency noise in its most common gradient form.

• Accenting lows sometimes produces "boomy" bass.
• Very susceptible to wind noise. Not suitable for outside use unless very well shielded.

Principle: sound pressure changes the spacing between a thin metallic membrane and the stationary back plate. The plates are charged to a total charge

where C is the capacitance and V the voltage of the biasing battery.

• Best overall frequency response makes this the microphone of choice for many recording applications.

• Expensive
• May pop and crack when close miked
• Requires a battery or external power supply to bias the plates.

A change in plate spacing will cause a change in charge Q and force a current through resistance R. This current "images" the sound pressure, making this a "pressure" microphone.