Microphone Polar Patterns...
What are they, and why do they matter?
The most important characteristic of any microphone is its directionality or “pickup pattern”. Any microphone exhibits its best frequency response when pointed directly at the sound source. The pickup pattern is not a physical component added to the microphone; it is by and large the result of how the capsule is constructed. There is no “ideal” pattern; the choice is often dictated by application.
When choosing a pattern, you should be aware of the phenomenon known as the “proximity effect”. Simply put, proximity effect is the change in frequency response as the microphone position is changed relative to the sound source. Depending on the pickup pattern, the low frequency response will increase, sometimes greatly, when positioned less than 12 inches away from the sound source. Understanding and knowing how to use the proximity effect can be a tremendous help in getting just sound you looking for. The following sections details the three most common pickup patterns.
Also referred to as unidirectional, the cardioid (“heart-shaped” – it shares its roots with the words cardio, cardiology, etc.) pattern is the most commonly used pickup pattern. The cardioid pattern is most sensitive to sounds directly in front of the mic, and rejects sounds coming from behind the microphone, preventing feedback from the onstage monitoring systems, plus the cardioid provides better isolation from other vocalists or instruments sharing the stage. The tradeoff when using a cardioid microphone is that they have a more pronounced drop in bass response and fidelity when moving away from the center axis of the microphone.