Getting rid of room noise...

  • Thread starter Thread starter bennychico11
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bennychico11

bennychico11

...
Don't worry, this isn't one of those "i have a computer in my room, how do I get rid of the noise?" :)

Rather, I was working on this project today (audio for video) where the video was shot inside a Sam's Club store. The client didn't have the money originally to have me work on the audio, so only video work was done on it. Needless to say they were disappointed in the audio when it was played back in a large theater. They said the rumble noise of the store was very distracting.
In the future they want to avoid this and the guy who recorded the audio said "well, they should have fixed it in Pro Tools"....of course, I couldn't because I never touched the project.
The location audio guy said next time he plans on trying to take another microphone faced 180 degrees the other way and place it coincident with the other mic. He thinks that doing so will help get rid of the noise when we blend the two together but also keep the voice normal (cancelling the noise out).
Assuming he means to use two shot gun microphones, I can't see that this will produce a better result because of a) how directional the shot gun mics are and b) how unpredictable room noise is.
I was able to show them that I can just simply EQ out mostly all of the rumble that would play back in theater subs.

Anyone think that his idea would work better? I'm sure they're going to come back to me and say "should we try this."
My recommendation was just to use a body mic along with the shotgun, but location guys seem to hate doing this.

:cool:
 
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Hey Ben,

I think he's trying to work in the theory that placing the mics like that will push their diaphragms in the opposite directions so when you sum them together you get a natural phase cancellation.

I've never tried it myself, so I can't vouch for how well it may or may not work. I'd tend to think that the mics had better be pretty darn well matched in both their response and polar patterns and gain, and would be somewhat sceptical as to how well it would work in practice. But I'm just specualting. It would be interesting to try.

G.
 
yeah, I understand what he's thinking in theory...but I just don't think it would work in practice.
The shotguns are made to reject almost everything that it's not facing at...so anything behind the mic isn't going to be picked up (not only the dialogue, but also the room noise that the other mic is hearing). So it would be capturing reflections of the speaker and it's own set of noise which probably isn't going to coincide with the noise in the first mic. As is the nature of complex sounds. Plus it also will pick up anything that is not in the shot (ie. the camera crew).

I don't know, supposedly this guy is well known within KC for audio, I'm just not able to picture it in my head actually working out (or working better than just putting a lowcut on the mic or EQing afterwards).

thanks Glen
 
bennychico11 said:
The shotguns are made to reject almost everything that it's not facing at...so anything behind the mic isn't going to be picked up (not only the dialogue, but also the room noise that the other mic is hearing). So it would be capturing reflections of the speaker and it's own set of noise which probably isn't going to coincide with the noise in the first mic. As is the nature of complex sounds. Plus it also will pick up anything that is not in the shot (ie. the camera crew).
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Yeah, the ambient noise would have to be fairly constant and consistant for that phase cancellation to work. It probably works fine with a couple of matched cardioids on standard room ambient noise, but I'm not sure of the nature of something as big and reflective as a Sam's Club. Maybe I'm over-thinking it, but I'd think that the size of the delays in the reverberated sounds might be an issue. On the other hand, the reverbs may be so bright and numerous that it all just winds up a pink wash that's fairly consistant anyway.

(The loudest of sounds anyway. Obviously if some worker drops a pallet in the background somehwere, there is going to be a rebverb delay that will not cancel. Then again, that's when the director yells, "Cut!" anyway :) )

I'm with you; I'd like the lapel mic/shotgun tag team. But maybe that's just because I have not learned enough location audio ninja tricks yet. They give away Oscars and Emmys for that kind of stuff.

Any chance that you can do a field test on your own before you take the next step inthe project? Maybe with a little secret homework you could ace it on the spot when the time comes ;).

G.
 
SouthSIDE Glen said:
Any chance that you can do a field test on your own before you take the next step inthe project? Maybe with a little secret homework you could ace it on the spot when the time comes ;).

G.
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yeah, good idea. I might actually try that tomorrow and see what I can come up with, if I have time.
unfortunately I think we only have one shotgun mic in the studio...hmmmmmmm
:)
 
with a decent (gun) mic, and more importantly, a good boom operator the background noise should be ok (good enough anyway)
what mic was used the first time?

going with a lav would probably not hurt a bit though.
 
In the future they want to avoid this and the guy who recorded the audio said "well, they should have fixed it in Pro Tools"....of course, I couldn't because I never touched the project.
The location audio guy said next time he plans on trying to take another microphone faced 180 degrees the other way and place it coincident with the other mic. He thinks that doing so will help get rid of the noise when we blend the two together but also keep the voice normal (cancelling the noise out).
Click to expand...

the more i read this, the less sure i am about this guy.
what are you going to do in post that's going to be more significant than a hi-pass, or simple things to that effect?

and that 180 works in math land, but i just don't see it doing much good in real life. if someone at 90 degrees drops a whatever, maybe..... but to me it just seems like it's a way to make sure that everything at 180 is picked up, and it wont cancel.
the more i think about it, the dumber that idea gets.
 
thanks giraffe
Exactly my thoughts. It was a Sennheiser shotgun last time. I told them what I thought about it and just said that using a body mic along with a gun is going to be much less of a hassle and much easier to work with in post than worrying about a theoretical idea that probably won't work (and probably will just amplify the noise instead)

-B
 
Ya, I was just kidding, I figured there wasn't the budget for that kind of post...
Hopefully your location guy uses decent mic technique/selection next time :)
Reminds me of the days when clients would come in with crapily shot Hi-8 and say "we want to fix this to look like film"...
 
Dr Biscuits said:
"we want to fix this to look like film"...
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"Okay, let me just push my 'Hollywood Film' button.....and presto!"



it's kind of like how people ask me "Yeah, we don't want to use the phrase 'This sale is only on Thursday'.....can you edit it so it says 'Come to our store this Thursday' ?????"

"Yeah, let me just use my magical fairy button that morphs words into other words"

:rolleyes:
 
honestly the easy solution (atleast in my limited experience) is dialogue replacement... call all of the actors back in to a studio environment and have them resay all their lines. most hollywood movies go though this and in loud envirnments it makes a huge difference. ...and IMO an actor who can't do it shouldn't be working anyway...

add new vocals,add a little reverb, add background noise, and volia!

It's time consuming but I've done it with amateurs with no problems.
 
Has the guy ever heard of a high-pass filter???

Maybe a notch filter tuned to the frequency of the offending noise while recording.
 
...I'd also like to add that shotgun mics are figure8 pickup pattern so they pick up just as well (basically) from the back as they do the front...
 
I'm sure it'd be nice, but many times there's just no budget/time for ADR especially on commercials with an agency that truly believes in a "magic button"... and is trying to save $...
Of course, I remember a friend of mine telling me HE (the editor) ended up doing the voice reads for BOTH characters on this horrible low buget spot, straight on the Avid, no reverb, Radio Shack mic... man, those were the days...
 
zekthedeadcow said:
honestly the easy solution (atleast in my limited experience) is dialogue replacement... call all of the actors back in to a studio environment and have them resay all their lines. most hollywood movies go though this and in loud envirnments it makes a huge difference. ...and IMO an actor who can't do it shouldn't be working anyway...

add new vocals,add a little reverb, add background noise, and volia!

It's time consuming but I've done it with amateurs with no problems.
Click to expand...

I know how ADR works. again, unfortunately this is impossible. a) because of cost and b) because these were not actors. It was a corporate video for Sam's Wholesale Club. This was an emotional awards video for the company and was filmed with someone telling a story about how someone in her family worked for the company and was killed by a drunk driver. Needless to say, there were tons of tears and emotional, heart tugging moments. Not something you could easily reproduce in ADR.

...I'd also like to add that shotgun mics are figure8 pickup pattern so they pick up just as well (basically) from the back as they do the front...
Click to expand...

Shotguns are not quite bipolar. They have a small lobe in back and on the sides, but are very directional in the front (depending on the freq. of course). Unless they have a switchable polar pattern, they usually are considered lobar or supercardiod.


Has the guy ever heard of a high-pass filter???

Maybe a notch filter tuned to the frequency of the offending noise while recording.
Click to expand...

exactly what I ended up doing. Using a hi pass and then a wide parametric to get a little bit extra of the low end. Helped a ton.

In the end, I think they were asking more about the noise of the entire store which was ALL frequencies....and obviously not possible without ruining the voice. We sent off a sample DVD today of what I could do for them.
 
ok... yeah... those live events are a little hard to redo :)
 
zekthedeadcow said:
...I'd also like to add that shotgun mics are figure8 pickup pattern so they pick up just as well (basically) from the back as they do the front...
Click to expand...

If this is true, then why cant you just dup the shotgun track and pan HL and HR and let it cancel itself out.....??? Dont reverse the phase on it like you would with a M-S setup....
 
soundchaser59 said:
If this is true, then why cant you just dup the shotgun track and pan HL and HR and let it cancel itself out.....??? Dont reverse the phase on it like you would with a M-S setup....
Click to expand...
As you describe it, all that would do is give you a strong ghost mono up the center, there's no cancellation.

G.
 
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