Boom

1) A boom is a long pole upon which a microphone is mounted to capture dialog and effects during the production of a movie or television program. The length of the pole allows the recordist to work far from the actors and out of the camera's view.

2) Boom also refers to the audio channel containing only low frequency information (less than 120Hz) in a multichannel configuration. This is also known as the LFE or Subwoofer channel.