We’ve all dealt with unwanted sounds when shooting on-location. We’re recording dialog and an air conditioner kicks on or there is a noisy freezer running in the background that ruins an otherwise good take. Exterior sounds can cause the same problem. In an ideal situation, we would turn off or unplug the offending sound and record another take. Unfortunately, that is not always an option.
Record at least 30 seconds of room tone or location ambience whenever you’re on a shoot. Getting the sound of the space where you are will be valuable later. Have everyone be quiet, leave the mic in the same position where you were set up for the dialog and then record. If you’re inside, record room tone with the air conditioner off and then on in the background. And then there’s the noisy refrigerator or freezer too. Get that background sound as well but leave the mic in the same location.