How polar patterns are made

Cardioid, hypercardioid, figure-8: the familiar patterns of microphones are not separate inventions. They are all blends of the same two ingredients, a pressure response that hears everything equally and a pressure-gradient response that hears best along one axis.

The recipe

An omnidirectional capsule responds to sound pressure at one point, so its sensitivity does not depend on direction. A figure-8 responds to the pressure difference across the capsule, which is largest along the axis and zero at the sides. Mix them and you get

sensitivity(θ) = a + (1 − a) · cos θ

where θ is the angle from the axis and a is the omni share. The sign matters: the cosine term is negative behind the capsule, so the rear lobe of a figure-8, hypercardioid or supercardioid has inverted polarity.

The family

The distance factor says how much farther a microphone can be from the source, compared with an omni, for the same ratio of direct sound to diffuse room sound.

Hypercardioid or supercardioid?

Both are tighter than a cardioid. The supercardioid has the narrower rear lobe and a better front-to-back ratio; the hypercardioid has the highest rejection of diffuse sound (the largest directivity index of all first-order patterns) but a stronger rear lobe. Pick the supercardioid when unwanted sound comes from behind and the hypercardioid when you want the greatest rejection of the room.

What the pattern does not do

• Real microphones change pattern with frequency: most are more directional at high frequencies and nearly omnidirectional at the bass end.
• Sensitivity at 90° off axis is not zero except for figure-8 patterns. A cardioid at 90° is 6 dB down, not silent.
• A tighter pattern has more proximity effect and, in general, more handling and wind sensitivity.

Try it

Pick any pattern and sweep the blend in the polar pattern viewer. The values for directivity index, null angle and −3 dB angle are computed from the same formula.

Draft: written by an AI assistant, awaiting technical review.