What Is a Polar Response Pattern?

Omnidirectional

• Omnidirectional microphones consist of a membrane, or diaphragm, fixed across the mouth of a sealed cavity. They are sensitive to variations in air pressure, or sound waves, but cannot detect which direction the sound is coming from. In other words, they are equally sensitive to sound coming from all directions. As such, they have an omnidirectional polar response pattern, drawn on paper as a circle, but actually a sphere.

Figure of Eight

• Figure of eight microphones, also known as bidirectional microphones, use a diaphragm that is open to the air on both sides. They are sensitive to differences in air pressure between the front and rear of the diaphragm, so pick up sounds from the front and rear, while rejecting sound from the sides. Their polar response pattern is drawn on paper as two conjoined circles, one to the front and one to the rear, resembling a figure of eight.

Cardioid

• Cardioid microphones use a combination of omnidirectional and figure of eight elements and are sensitive to sound within 120 degrees of the direction they are facing. Sound coming from the front of the microphone is picked up by both the omnidirectional and figure of eight elements, while sound coming from the sides is picked up only by the figure of eight element. Cardioid microphones take their name from their polar response pattern, which resembles an inverted heart; the prefix ̶0;cardio̶1; is derived from the Greek word ̶0;kardia̶1;, meaning ̶0;heart.̶1;

Hypercardioid

• So-called hypercardioid microphones are similar in design to cardioid microphones, but are more directional and have a tighter polar response pattern, which covers sound within 100 degrees of the direction they are facing. Hypercardioid microphones reduce feedback -- whistling noises caused by electrical oscillation -- and reject sound coming from the sides better than their cardioid counterparts. They are often used to isolate one sound, such as a quiet vocal, in an otherwise loud environment. Unlike cardioid microphones, hypercardioid microphones also pick up some sound from the rear, so their polar response pattern is somewhere between that of cardioid microphones. When drawn on paper, it typically consists of an inverted heart-shaped lobe to the front and a smaller, almost circular lobe to the rear.