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Acceptable DB Level For Mic Noise?

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Richard ChristyAcceptable DB Level For Mic Noise?
by on Sep 8, 2011 at 5:11:31 pm

I have a lav mic I'm using on a speaker. We're in an enclosed room, about 12x7 with your typical furnishings (carpet, furniture, etc...) The only thing running is the PC we're recording on and it's across the room, under a desk (so the noise from this is marginal).

I took a sample of him speaking, then he pauses for a moment, then he starts speaking again. I dropped this section into Soundbooth and isolated the silent part in-between during his pauses.

The noise level here is jumping at around -50db to -45db. I will be applying noise reduction filters to this over all VO file in post, but I was just wondering if we are starting off with a decent noise level? Are we registering to much noise in the raw audio? Should we attempt to reduce this or is this a good starting point?

Also, the noise is not coming from movement but just pure "frying" from the mic, as one often gets. Also, it's not very audible in the file unless you normalize it.

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Joseph W. BourkeRe: Acceptable DB Level For Mic Noise?
by on Sep 9, 2011 at 3:23:24 pm

Richard -

Are you sure the noise floor in the room is only coming from the PC? Often times there is air conditioner rumble, especially if you're in an office building, and machine noise from other rooms vibrating through the walls and ceilings.

In a way, it doesn't matter where the noise is coming from. The important thing is to isolate the noise floor (from points in the clip where the speaker is silent - which you're doing), and then remove it from the audio.

The frying noise you're talking about - could this be a battery in the mic on its' way out, or is it just a cheap lav mic? Another thing to check is the gain on your mic while you're recording - is that coming through a mixer with a master volume? You might be introducing noise there as well. There will always be some noise in the audio, due to ambient sources and RF interference, and a million other possibilities. The key is to track down the ones you can control before you record, and remove the ones you can't in post. Since every audio recording situation is different (unless you're in a studio), and mics are all over the place as far as signal/noise ration, there is no useful number in db to give you.

Joe Bourke
Owner/Creative Director
Bourke Media

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Richard ChristyRe: Acceptable DB Level For Mic Noise?
by on Sep 12, 2011 at 6:23:01 pm

Yes, I see what you mean. And upon furthering investigation it looks like frying was the wrong word to use. It sounds more like an air conditioner vent. However, we have no air of any kind running and the only other thing that can generate this type of noise is the fans and hum of the PC, which even across the room is quite noticeable.

I'm also finding that by using the Spectral Frequency Display to isolate that bit with the marquee tool and capture a noise print, I'm able to use Soundbooth's default "reduce by" settings in the Reduce Noise process to almost completely remove it without effecting the tone of the voice.


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