Matching Ambient Sound
Matching ambient sound means recording sound separately from any video, but in such a way that it can be matched with the video shots if required. This is useful for patching up mistakes, creating a consistent background noise, and adding new audio.
Note that the sound does not necessarily have to be synchronised with the pictures, just matched. This means it does not need to include specific sounds on cue (e.g. a hammer striking a nail), it is only required to match the general expectations of the scene (e.g. background construction noise).