What characteristic best defines a unidirectional microphone?

A unidirectional microphone is specifically designed to capture sound primarily from one direction while minimizing sound from other angles. This characteristic makes it particularly effective in situations where you want to focus on a particular sound source, such as a speaker or an instrument, while rejecting background noise that might come from other directions.

This directional sensitivity is beneficial in various recording and performance settings, as it helps to produce clearer audio by isolating the desired sound source. The technology behind unidirectional microphones often involves specific design elements, like a cardioid pattern, that enhance this directional sensitivity.

The other features mentioned in the choices do not inherently define a unidirectional microphone, which is why they do not accurately represent its primary characteristic.