What are Bidirectional Microphones?

Bidirectional or figure-of-8 microphone

Bidirectional microphones (also called figure-of-eight microphones) are microphones that pick up sound well, or with high sensitivity, from the front and back but poorly, or with low sensitivity, from the sides.

The above illustration shows a bidirectional microphone sound pick-up pattern. This pattern shows that a bidirectional microphone picks up lobes of sound of equal sensitivity on opposite sides of the diaphragm (front and back) and steep nulls at right-angles to the diaphragm (the sides).

Bidirectional microphones are used in applications where sound is recorded from the front of the micrphone and back of the microphone, but not the sides. An example of this is a Q&A lecture or presentation, where a professor gives a lecture to an audience and accepts questions from them. A microphone needs to pick up the speech of professor from the front and the questions asked from the back in the audience. This is a practical example of where bidirectional microphones are needed.

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Types of Microphones