Polar Patterns
Description
The polar pattern of a microphone is the area around the microphone that it is most sensitive to. The areas of sensitivity, and their descriptions, are listed below. Some microphones can have more than one pattern of sensitivity which can be selected with a switch on the microphone.
Omnidirectional:
Microphones of this type can pick up sound, more or less, equally from all directions. This allows you to record everything in the room, which may or may not be desireable. One thing to note is that omin mics tend to have a smoother frequency response and can sound more "natural" then cardioid mics.Cardioid:
Cardioid microphones pick up sound from directly in front of the microphone, and are not nearly as sensitive to sounds coming from other directions. This gives the ability to point the mic at your desired sound source and exclude sounds coming from other directions.Supercardioid:
Similar to the Cardioid microphone but with an even smaller area of sensitivity directly in front of the mic.Hypercardoioid:
Again, similar to the Supercardioid with an even smaller are of sensitivty. Hypercardioid mics are often used in movie/video filming because they can pickup sound reasonably well at modest distances. In this scenario, they are often called "shotgun" mics because they often resemble the barrel of a shotgun.Figure-Eight (Bi-directional):
So called figure-of-eight mics have areas of equal sensitivity on opposites sides of the mic element. Think of it as two opposed cardioid patterns, which ressmble a figure-eight when drawn on a diagram (see illustration). The figure-eight pattern is useful if you need to pickup sound from two vocalists standing on opposite sides of the microphone, for example. And, a pair of them provides a very natural stereo field when used in Blumlein configuration.
Examples:
Omnidirectional Mics pick up sound from all directions.
An example is the Shure VP64A, a dynamic mic.
Also, the mics from Earthworks must be considered, which are every high quality small-capsule condenser mics, many of which are omni, such as the QTC40.
Cardioid Mics, arguably the most common type, are represented by Shure SM57, SM58, SM7b, and ElectroVoice RE20.
SuperCardioid Mics tend to be used in more specialized situations, such as movie sets and live sound, because of their rejection of unwanted sound outside fo the pickup pattern. An example is the Rode NTG4 Shotgun mic which is used extensively in video recording.
Multi-Pattern: And we must mention the many mics that have multiple polar paterns selectable by a switch on the mic body. Examples include AKG C414 and Neumann U87.
Polar patterns can be leveraged to record only the sound you want. An omnidirectional mic will pick up sound equally coming from all directions, which is fine if you are recording something in isolation. But in typical recording situations, with multiple sound sources, guitars, vocals, drums, etc., you are trying to keep those sounds as separate as possible. So, typically you will use cardioid microphones, pointing the mic at the desired sound source, and the "back" of the mic toward any sounds you do not want to pick up. In this way, the polar pattern of the mic assists in capturing the sound you want, and rejecting the sound you don't want.
In the photo we see two mics are being used, a Shure SM57 and an AKG C414, to record a guitar amp. Two mics are used here to get a choice of different sound because the two mics are very different. Either, or a combination of both, can be used in the mix. However, a single SM57 is a very common way to mic a guitar cabinet, and, is, in fact, the way many songs are recorded.