Polar Patterns

A microphone's polar pattern sets what it hears from each direction, and with it bleed and proximity effect.

Related

Polar PatternMicrophoneDrum Kit

The problem

A microphone is most sensitive in front but still hears the sides and rear. That pattern sets bleed, proximity effect and room in the capture. Before placing it, decide what to pick up and what to avoid.

Signal chain

A cardioid uses one diaphragm and an acoustic delay at the rear, creating a null behind. An omnidirectional capsule has no proximity effect and a flatter low end. A figure-eight is out of phase on the two sides and also null at the rear; it suits two singers facing each other or side isolation. A switchable pattern uses two diaphragms and changes their polarisation.

Placement and settings

Aim the cardioid axis at the source, with a singer 15 to 25 cm away; closer than that, proximity effect inflates the low end. Use omni for a choir or room sound at one metre. With figure-eight, put the source in one lobe and aim the other at what you want to reject.

What to listen for

Walk a full circle around the microphone while clapping, and hear how level and tone change. Move in close and speak, listening for a thicker low end. Turn the cardioid to 180 degrees and check that the null is quiet.

Common misconceptions

• Cardioid rejects everything behind it → low frequencies diffract around the body, so the rear is not silent.
• Omni has no proximity effect → correct, which makes its low end easier to control.
• Pattern only changes level → off-axis response changes tone as well.

Sources

• Eargle, The Microphone Book, 3rd ed., directivity and proximity chapters
• Olson, Acoustical Engineering, pressure-gradient microphone theory

Used for fact-checking only; all prose is original.