I just got finished shooting this movie and I should have known better - The movie was shot in a bar and over the bar was a giant air conditioning unit that the naked ear could not hear and my sound guy said the sound was fine but now I am cutting the movie all you can hear is the air conditioning humming over the dialogue - its constant through the whole clip. I have tried noise reduction on some crappy freeware but it reduces the dialogue also. I just need the hum removed. Any suggestions? I see other posts mention Sony Noise Reduction but that might be out of my price range. I need the cheapest way possible. Anything to remove the hum entirely or lower it would be great.

Thanks

Bias SoundSoap is about $75 and works well in many cases.

Are you sure it isn't coming from another cause like a ground loop hum or other electrical problem? That could change the way you go about setting your noise reduction software for best results, but it's not a major issue. It would be good to know for absolute sure for future work, since it seems that it wasn't recognized on the set. If the sound guy was monitoring from a mixer and not the camera and the sound was ok, then it could have been a connection problem between the mixer and camera.

Most NLE's have at least some simple filtering. If the noise is low frequency rumble a simple hi pass may suffice. If it is narrow band (true hum or tone) a notch or band reject should do the job.

Redoing the dialog (ADR) will always solve the problem if that is practical.

As Steve suggested, SoundSoap is very good at removing AC and other "broadband" noise. If you want to email me a 20 second or so sample I'll Soap it and send it back. If you do, try to find a clip that includes about two seconds or more of nothing but the noise.