The electrical and acoustical characteristics of a microphone determine the quality of performance and usefulness for a specific application. No one factor determines the quality of the microphone, all parts work together, and it is important to understand the sum of the qualities is what you need to look for. After all, if the sound source sounds bad, no microphone in the world will make it sound better.
Microphone Pickup Patterns (Polar Patterns)
Transduction is not the only way to categorize microphones; you must also take into account the pickup pattern for each individual microphone. The pickup pattern will give you more understanding when placing the microphone, because the pattern will show you where the microphone element is more sensitive to the sound source.
The cardioid pickup pattern is quite possibly the most popular pickup pattern available. The pattern is called “cardioid” because it is in more or less a heart shape, and it is most sensitive to sound coming from the front (primary axis), and rejects sounds from the rear and sides of the microphone. This polar pattern makes cardioid microphones ideal in live sound, as they reduce feedback and can potentially increase system gain.
One drawback of the cardioid pattern is that if has a tendency to colorize the sound source, because the frequency response differs the more off axis it gets. Cardioids are popular in the studio because they can reduce or eliminate sounds arriving off axis of the desired sound source. The rough frequency response of cardioid microphones can be more sensitive to pops and breath noise than an omnidirectional pickup pattern.
Omnidirectional microphones pick up sound from all sides. The Omnidirectional pattern is normally not used outside the studio because it offers no protection from feedback or other sounds in the environment, but not always so. Omnidirectional microphones a good low frequency response, and are less likely to pick up breath and wind noise. The microphones with the omnidirectional pattern also have a smoother frequency response than directional microphones, so there are fewer peaks to cause feedback, so a high quality omnidirectional microphone may be more useful than a lower quality directional microphone in some cases. The omnidirectional microphone’s home however, is in the studio.
The bidirectional pickup pattern is in an unusual, but often very useful pickup pattern. This pickup pattern is names for obvious reasons, as is picks up sounds from the front and back equally, and reflects from the sides equally. The Bidirectional is useful when you want to capture two separate sound sources with one microphone where controlling each sources volume is not a factor. This would include placing a bidirectional microphone between 2 toms on a drum set, two vocalists, etc.
The Supercardioid is an extremely directional element. In contrast to the cardioid, the supercardioid has more rear pickup, but is still small, causing it to pick up more sounds coming at the microphone from the rear than the cardioid. The supercardioid does however, have a tighter frontal pickup pattern which increases rejection on the sides of the element. Because of the tighter frontal pickup pattern, the supercardioid may be used to capture sounds that are distant, such as a shotgun microphone.