Microphone polarity and polar patterns are vital knowledge
to any that seek to enter the field of sound design. Microphones are critical
tools of the trade that see use on a near constant basis. The knowledge of
polar pattern properties can allow a sound designer to maximize the
effectiveness of a smaller number of microphones and increase the quality of
recordings. Polar patterns fall into a number of categories; cardioid,
hyper-cardioid, bi-directional, and omnidirectional.
Omnidirectional microphones record 360 degrees around the
capsule of the microphone with minimal phase cancelation. Many times these
microphones are used as room microphones, as they capture much more than single
sources. These microphones are also useful for recording orchestras.
Bi-directional microphones or “figure 8” microphones have a polar pattern
that extends to the front and rear of the capsule with maximum phase
cancelation at the 90 and 270 degree positions. Bi-directional microphones were
once very popular as the standard configuration for ribbon microphones, which
continues to this day.
Cardioid polar patterns are the most common polar patterns
on the market. Cardioid polar patterns have a maximum sensitivity at 0 degrees
to the capsule and maximum rejection at 180 degrees to the capsule. There is
typically a gradient of phase cancelation between 0 and 180 degrees. Cardioid
polar patterns are most closely associated with dynamic microphones, though are
commonly found on condenser microphones as well.
Hyper-cardioid polar patterns are a relatively recent
addition to the list of polar patterns. Hyper-cardioid polar patterns are very
similar to cardioid polar patterns; however the maximum rejection at 180
degrees to the capsule is replaced with another lobe of sensitivity. This
allows the 0 degree sensitivity to be more selective and allow greater
rejection off axis.
Knowledge of polar patterns allows recording engineers and
sound designers to select the best microphone for the job in much the same way
a carpenter selects the most appropriate tool. Understanding of polar patterns
increases the quality of recording and allows for more streamlined production.
Therefore it is imperative that all audio professionals understand this vital
concept.
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