ADR is additional dialogue recording. You do this when your audio doesn't come out right. Usually that means during post-production you drag your actors into an ADR studio and have them watch the clip with bad sound and try to say the lines exactly the same. On low budget movies I've heard of people recording ADR in their room with blankets up on the walls and such to dampen the extra sounds. The foam backed boards would work well for this sort of thing.

There are also times on location when you just know the sound sucks and can't wait all day for the wind to die or whatever. In that sort of case it would be possible to do the ADR in the production vehicle if you have the right equipment. It can be less of a hassle than going back for it afterwards, at least that's the theory, I haven't gotten to the ADR step in my own production so I'm not certain but I wish I would have tried a couple of times because scheduling the actors will be a pain.

RJSchwarz
San Diego, CA