What is a Boom Microphone?

When you sit down to watch a movie filled with witty dialogue and action in the same scene, do you ever stop to wonder how they recorded that sound? Say the characters are walking down a sidewalk chatting... where's the microphone?

The answer is the boom microphone.

Shotgun microphones are designed for very specific sound pickup, excluding audio coming from the left and right, focusing only on what it's pointing at.

For more information, see Wikipedia.

Boom microphones are the mainstay of audio capture on film sets. Mounted on the end of a long, telescoping pole, the microphone is manned from afar, and hung over the head of the performer it's targeting.

Shotgun mics are the most commonly used, due to their exclusive audio pickup pattern. But when the camera angle is particularly tight, a cardoid microphone (Nearly spherical pickup pattern) can be used for a smoother sound.

A boom operator (the crew member who manages a boom mic) must hold the microphone very still, and usually a shock mount is employed to ensure no vibrations disturb the microphone during recording.

In smaller productions, the boom operator will also take over the job of audio technician, and monitor the audio as he records it.

While many microphones have thin foam windscreens, this often does not cut the wind enough for a filming session. In these cases the boom mic is covered with what is known as a dead cat (or dead kitten for smaller microphones). This is a furry sock-like cover for the microphone that cuts the wind and helps get a clearer recording.

Making a boom microphone is simple enough for the amateur film maker. All that is needed is a microphone (preferably shotgun pattern) with a long cord, and a pole. A shockmount is not needed but if you're willing to go to the extra effort there is a cheap alternative.

The boom pole can be any long pole, but here is a link for something a little more functional.