Several different microphones have been designed throughout the years to accomplish very different tasks. Some — such as condenser microphones — pick up a great deal of sound from several directions, while others pick up one focused sound only from one direction. Of this latter group, the cardioid microphone is perhaps the most popular, as it picks up almost exclusively the desired sound while ambient noise is hardly noticeable. It gets its name because of its pattern of sensitivity, which is roughly shaped like a heart when drawn out on an axis. This means that most of the sound it picks up comes from the front of the microphone, while minimal noise is picked up from the rear and only marginal noise is picked up from the sides.
This type of sensitivity pattern makes the cardioid microphone useful in many situations, including those in which several mics are being used at one time, live performances, and certain recording purposes. It may be a condenser microphone, which uses a capacitor system to pick up sound, or a dynamic microphone, which uses a coil attached to a diaphragm. When the diaphragm vibrates, it moves the coil, which then creates electromagnetic induction.
As a unidirectional microphone — that is, one that picks up sound from only one direction — this microphone is designed to pick up one sound well, with other ambient noises fading into the background. If this microphone still doesn't do enough to eliminate ambient noise for a user's purposes, the supercardioid microphone eliminates even more noise from directly behind the microphone. The supercardioid mic is often confused with the hypercardioid microphone, which actually does not eliminate as much noise behind the microphone, but eliminates more to the sides. Out of the three types, the hypercardioid is considered the most directional.
For musical purposes, the cardioid microphone is particularly useful for live sound, such as concerts. It can also be used as a vocal mic for presentations, public address, and other situations that require a vocal mic. The style is also a good choice for recording concentrated sounds, such as vocals and certain types of drums.
Other situations in which a cardioid mic may be used include household applications, such as in a telephone. The microphone in the handset picks up primarily the speaker's voice while eliminating other ambient noise, such as background conversation or television chatter.