Microphones

A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. Electromagnetic transducers facilitate the conversion of acoustic signals into electrical signals. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, two-way radios, megaphones, radio and television broadcasting, and in computers for recording voice, speech recognition, VoIP, and for non-acoustic purposes such as ultrasonic checking or knock sensors.

Most microphones today use electromagnetic induction (dynamic microphones), capacitance change (condenser microphones) or piezoelectricity (piezoelectric microphones) to produce an electrical signal from air pressure variations. Microphones typically need to be connected to a preamplifier before the signal can be amplified with an audio power amplifier and a speaker or recorded.

Polar Response

The way that a microphone picks up sound at different angles is referred to it's polar response. Different types of polar response are useful for different applications.

Cardioid

The most common type of polar response, "cardioid" microphones generally pick up sound best from the front, and worst from the back. Useful for your shitty let's plays, when you would only have one person talking over a game of Yahtzee.

Omnidirectional

Less commonly found than cardioid, but also useful. Omnidirectional microphones pick up sound equally well all around it. Useful for situations where you would intend to use a single mic to pick up sounds all around a room. (ex. a porno, a group let's play (don't))

Bi-directional

Similar to cardioid, except the mic will pick up sound equally well from both it's front and it's back.

Frequency Response

Same situation as in frequency response for headphones, except in this situation, frequency response is used to show what frequencies the microphone is able to pick up, rather than reproduce. If you're to purchase any mic that's half decent, a frequency response chart will likely be included on paper with the mic. If not, it can probably be found online.