OMNIDIRECTIONAL SENSITIVITY PATTERNS
A microphone's directionality pattern can be described in terms similar to what we use for antennae. Its sensitivity can be measured as a function of direction. Microphones can be classified as omnidirectional (nondirectional) and directional (e.g., bidirectional and unidirectional).

The polar response of an ideal omnidirectional microphone is: A cross-sectional view of the microphone: reveals that the diaphragm is designed to be sensitive to signals emanating from any direction.