When doing live sound work, different microphone polar pickup patterns will dictate where stage monitors should be placed for best feedback rejection. For example: A cardioid pattern microphone has best sound rejection directly behind the mic (place the monitor right in front of the singer). A hypercardioid mic actually has two dead spots, one at around 160 degrees, and the other around 200 degrees off-axis from the mic capsule (place the monitor in front, but slightly off to the side of, and angled back at the singer). Placing a monitor directly in front of a singer using a hypercardioid mic will invite feedback.
Corollary to today’s tip: The above information also holds true when you are trying to minimize leakage of sound in the recording studio. Clever and thoughtful placement of microphones with the right polar patterns will greatly help in controlling microphone bleed.