What does the "Mic NR" actually do ? at DVinfo.net

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Old September 23rd, 2003, 10:24 AM   #1
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What does the "Mic NR" actually do ?

I have been wondering recently about this :
does anyone know what exactly the function "Mic NR" provides ? I assume it's different from a simple "Low Cut" (that can be found anyway on the XLR mount), and I've heard it helps preventing the little noise produced by the camera itself from being heard on the tape. I have tried it : seems to be working quite well but I still don't know what part of the audio spectrum you acutally loose when you switch it on. Is it aimed at a specific frequency ? Would it sound wiser to remove the camera noise (which you get anyway with a mic fixed on the standard mount) in the post ?

Cheers,

JDB
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Old September 25th, 2003, 06:07 PM   #2
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The Mic NR setting seems to apply some kind of inverse phase signal to the audio so as to cancel out the motor noise. A very smart little trick indeed. And it seems to be adaptive: if you turn it on but there is no camera noise present, like when using an external microphone, nothing happens. Still, Sony recommends you turn it of when not using the on-camera microphones.

You can hear this inverse signal for about half a second when you have the input level set up high and unplug or turn off a microphone. Beware though that if the level is set too loud unplugging or turning something off will generate a transient that can ruin your headhones, your speakers or your ears so don't go too high with the gain and/or output level.
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Old September 26th, 2003, 11:15 PM   #3
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All i know is you have to be carefull with it as you use external mics (including the top mounted shot gun). I ran into some problems with it as i was conducting some interviews (the problem was present for the shotgun and a lav mic). The room was rather quiet so the NR was doing it's thing, but once the talking happened it would turn off as the level rose above whatever threshold it has set and i would get the talking and the white noise that the NR was filtering. ( i guess it's like a noise gate filter) I was really annoying because it sounds like a buzzing turning on and off. Really it was the NR turning on and off filtering the white noise in and out with the persons voice. It was killing me. you can really only hear it while monitoring with headphones. I finally figured out that it was the NR. So now i turn it off and get a steady buzz from the room noise and it sounds way better. I'll take consistant noise over in and out silence. but maybe i'm wrong.
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Old September 27th, 2003, 07:11 AM   #4
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In fact, I only used it when I had to record low level sound (countryside sound, birds filying on the fields etc...), so I haven't had any problem yet with people talking as you mention. Anyway while doing interviews in the future, I'll anyway try as much as possible not to use it (meaning : having a mic placed closer to the talking person, which is and remains the best of course).

I am now shooting a documentary in foreign counrties, but once at the editing, I'll have to see if the motor noise is somehow "removable" with an audio filter (I guess the motor of the camera must have some fixed frequency you should be able to target with a good filter)...
if you have any idea about it ?
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Old September 27th, 2003, 11:15 AM   #5
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here's a noise reduction article that may help you. You'll have to register for the free site to read it though.


http://www.dv.com/features/features_item.jhtml?category=Archive&LookupId=/xml/feature/2003/rose0903_feature
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