A microphone, sometimes referred to as a mike or mic is an acoustic-to-electric device or sensor that converts sound into an electrical signal. Normally they are a very sensitive instrument.

Microphones are used in many applications such as telephones, tape recorders, security systems, hearing aids, motionpicture production, live and recorded audio engineering, in radio and television broadcasting and in computers for recording voice, VoIP, and business audio/video conferencing. They can also be used for monitoring purposes in industry and society in general.

A microphone is a device that translates sound waves into an electrical signal. The most common design uses a thin membrane which responds to variations in sound waves by vibrating in response to those sound waves and subsequently translates them into an electrical signal. Most microphones in use today are for audio use, electromagnetic generation (dynamic microphones), capacitance change (condenser microphones) or piezoelectric generation to produce the signal from mechanical vibration.

Electret condenser microphones

An electret microphone is a relatively new type of capacitor microphone. An electret is a ferroelectric material that has been permanently electrically charged or polarized. The name comes from electrostatic and magnet; a static charge is embedded in an electret by alignment of the static charges in the material, similar to the way a magnet is made by aligning the magnetic molecules in a piece of iron. They are used in many applications, from high-quality recording and lavalier use to built-in microphones in small sound recording devices and telephones. These microphones can be especially useful when conducting a seminar or for people who work in journalism. Though electret microphones were once low-cost and considered low quality, the best ones now equal capacitor microphones in every respect and can even offer the long-term stability and ultra-flat response needed for a measuring microphone. Unlike other capacitor microphones, they require no polarizing voltage, but normally contain an integrated preamplifier which does require power (often incorrectly called polarizing power or bias). This preamp is often phantom powered in sound reinforcement and studio applications. A lavalier microphone is made for hands-free operation. These small microphones are worn on the body, often concealed, under a collar, or held in place either with a lanyard worn around the neck or a clip fastened to clothing. The cord may be hidden by clothes and either run to an RF transmitter in a pocket or attached to a belt (for mobile use), or run directly to the mixer (for stationary applications). Note that a term that is often used in place of lavalier microphone is lapel microphone.

A wireless microphone is one which does not use a cable. It usually transmits its signal using a small FM radio transmitter to a nearby receiver connected to the sound system. Also very appropriate for use as a lapel microphone.