What is microphone polar pattern? (Part 1: Omnidirectional)
Answer: One of the most important distinguishers of a microphone is its polar pattern, a graph that conveys the mic’s directional properties. Most microphones can be placed into one of two main groups: omnidirectional and directional. Omnidirectional microphones are the simplest to design, build and understand. They also serve as a reference against which each of the others may be compared. So we’ll start our polar pattern discussion by looking at omni mics.
Omnidirectional microphones pick up sound from just about every direction equally. They’ll work about as well pointed away from the subject as pointed toward it, if the distances are equal. However, even the best omni models tend to become directional at higher frequencies, so sound arriving from the back may seem a bit “duller” than sound from the front, although apparently equally “loud.”
The physical size of the omnidirectional microphone has a direct bearing on how well the microphone maintains its omnidirectional characteristics at very high frequencies. The body of the microphone simply blocks the shorter high-frequency wavelengths that arrive from the rear. The smaller the microphone body diameter, therefore, the closer the microphone can come to being truly omnidirectional.
Omni mics will pick up all of the reverberation and echoes in a room, resulting in a very “live” sound. Thus, as long as the environment isn’t too noisy, omnis can provide a nice sense of a space’s atmosphere, and are often preferred for their flatness of response and freedom from the proximity effect that can be an issue with close-up directional miking. (We’ll address proximity effect in greater detail in Part 2 of this series.)
Omnidirectional microphones are normally better at resisting wind noise and mechanical or handling noise than directional microphones. Omnis are also less susceptible to “popping” caused by certain explosive consonants in speech, such as “p,” “b” and “t.”
Serious recordists will undoubtedly want to have both omni and directional microphones available to be ready for every recording situation, so in our next post we’ll take a look at directional mics. Until then, if you have questions about microphones or other A-T gear, please contact our Audio Solutions Department for personal assistance.