There are a number of ways to classify the different types of microphones. They are often distinguished by the directional pattern, in which they pick up sound, or by the type of transducer they have. Another common way, though it may be considered too general for most purposes, is to categorize them by portability, or simply according to their specific purpose.
Among the most general ways of classifying microphones is to look at one of two categories - wireless and wired units. Those that are wireless can transmit their signal to an amplifier with a wireless receiver, usually a radio frequency. Transmission requires an on-board power source, usually a standard battery. Some types use rechargeable batteries. With a wired microphone, both the power and the audio signal must be transmitted through a cable.
As mentioned previously, microphones are also classified by the directional pattern. This is very helpful information for those who need the capability of picking up sound or ignoring sound from specific directions. The most common directional microphone is the cardioid, which picks up sound in mainly a 180-degree half circle. There is also a small spot directly behind the microphone where sound can be picked up. The uni-directional microphone picks up sound only from one direction and the omnidirectional picks up sound in all directions.
In addition to these major types of microphones, there are other directional options as well. Usually, they are a variation of one of the types already mentioned. For example, there is the super or hyper cardioid, which can pick up sound very well from directly in front or directly behind. A bin-aural, or bi-directional microphone can do the same thing, but from either side. This is especially useful for producing stereo recordings.
The other common way to classify types of microphones is by differentiating the various transducers. Capacitor mics, for example, use DC electricity to polarize internal plates, which are used to convert sound to energy. Dynamic microphones, by far the most popular choice, make use of a coil within a magnetic field. The sound vibrates the coil which produces the energy. Electret microphones use a plastic piece that carries a permanent charge as the transducer, and ribbon microphones use a very thin piece of aluminum for the transducer.
Different types of microphones may be used in a wide variety of situations. For example, dynamic, cardioid units are commonly used for live performances. Ribbon mics are used for studio recording, where there is less chance of them becoming damaged. Bidirectional microphones may be used in radio and television studios.