Muffling unavoidable background noise? at
DV Info Net

Go Back   DV Info Net > The Tools of DV and HD Production > All Things Audio

All Things Audio
Everything Audio, from acquisition to postproduction.

Thread Tools Search this Thread
Old October 22nd, 2009, 03:39 PM   #1
Join Date: Jan 2009
Location: Washington, DC
Posts: 4
Muffling unavoidable background noise?

I produce a podcast with my company and we shoot in one of our offices with a simple set. We've got some good equipment (Sennheiser ew 100 G2 mics, an Edirol mixer) that picks up voices great but it also catches the sound of the building's AC. It can't be shut off in just one office, unfortunately. The noise it creates is this constant, low, wind-like sound that's sometimes accompanied by a high-pitched, somewhat squeal-like sound.

What I'm wondering is if there are any suggestions as to how to mask the sound either in the room (we've thought of foam padding but are not sure if we can get away with it in our building) or if the mics can be set better to help eliminate the sound or if its best to do so in post (I've used Soundtrack Pro and FCP using things like Hum Remover but that only goes so far).

Any help is greatly appreciated!
Lisa Mathias is offline   Reply With Quote
Old October 22nd, 2009, 04:15 PM   #2
Inner Circle
Join Date: Jan 2003
Location: Chicago, IL
Posts: 6,609
AC is a constant type noise. Record some room tone before you start the real shoot and then using one of your audio programs you should be able to pull a noise print of that noise then use either your NR program OR graphic EQ to find the frequency and drag it down to eliminate it without changing the tenor of the voices. I eliminate most AC noise by using a preset in my track EQ in Vegas and adjust accordingly. AC is a very low freq noise but it can be gotten rid of. The key is getting that noise print before hand.

I could be wrong but I don't think padding the room will help get rid of that noise although it might help the audio person when they bang their heads againt the wall while getting rid of the noise ;-)
What do I know? I'm just a video-O-grafer.

Last edited by Don Bloom; October 22nd, 2009 at 04:30 PM. Reason: meant to say DON'T not DO...oops
Don Bloom is offline   Reply With Quote
Old October 22nd, 2009, 04:27 PM   #3
Regular Crew
Join Date: Jul 2009
Location: Asheville NC
Posts: 182
First of all, the mics you're using are good, but they are omni-directional, meaning they pick up sounds from everywhere in the room, including the air handling ducts. Not much you could do with mic placement to help, I think. You said this is mostly a low rumble, and sometimes a high pitched squeal. Cutting the extreme low and high frequencies on the mixer may help. Optionally, you could do this more surgically in post.
The trick would be finding the offending frequencies (try the Voxengo SPAN plugin. KVR: Voxengo SPAN - Virtual Effect Its a free spectrum analysis software. You should be able to use that to see where the offensive frequencies are). Once you've found the source of the problem, you can dial in a parametric EQ to those frequencies in post and tone them down a bit. It will take a bit of playing around to mitigate the noise without making the voices sound unnatural.
One other option would be to place some heavy moving blankets over the air ducts if they are on the floor. You may have to weigh them down with something (sand bags, books, anything heavy). If the ducts are on the ceiling or wall, this might not be possible. Best of luck! Andy
Andy Balla is offline   Reply With Quote
Old October 23rd, 2009, 06:19 AM   #4
Inner Circle
Join Date: Sep 2006
Location: Sydney.
Posts: 2,847
Try recording some room tone (maybe at night but with aircon noise) lay it up adjacent to the length of the voice track and throw it 180d out of phase.

Raise and lower its level while examining what it does to your voice sound, if the aircon is low frequency enough it should be Ok for podcasting.

When you’re in a group photo always stand camera left, that way in the list underneath your name will be first.
Allan Black is offline   Reply With Quote
Old October 23rd, 2009, 01:38 PM   #5
Regular Crew
Join Date: Feb 2009
Location: Bothell Washington
Posts: 174
You need to move your mikes closer to the talents voice and reduce your gain. A mic will pick up a voice and room noise if it is placed mid chest level. By moving it up closer to the collar and having your talent speak up you compensate by lowering your levels and reducing your mic pick up of any ambient room noise.
Mark Boyer is offline   Reply With Quote
Old October 23rd, 2009, 03:45 PM   #6
Regular Crew
Join Date: Sep 2009
Location: Fresno,CA
Posts: 42
Tighter (directional) type mics
Position closer to talent (source)
Use Low Cut filter aka: High Pass
Possibility of aiming mic at source which is in front of a non-reflective surface
Zack Allen is offline   Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

B&H Photo Video
(866) 521-7381
New York, NY USA

Scan Computers Int. Ltd.
+44 0871-472-4747
Bolton, Lancashire UK

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > All Things Audio

Thread Tools Search this Thread
Search this Thread:

Advanced Search


All times are GMT -6. The time now is 01:28 PM.

DV Info Net -- Real Names, Real People, Real Info!
1998-2021 The Digital Video Information Network