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How do you combat fluctuating lav mic levels?

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David PayneHow do you combat fluctuating lav mic levels?
by on Nov 12, 2014 at 9:52:17 am

Hi all I have replaced my lav mics with some more reliable ones but they seem more directional which leads of a drop off in levels when somebody turns their head. I've always applied a dynamics effect in premiere pro cs5 and set the limit to -.05dB thinking that if I then audio gain the whole clip, it will boost the quiet parts but still limit the louder parts not to go above this level, however the age old problem that i've actually posted about in the past and never got anybody to confirm they have the same issue is this...

If somebody speaks loudly, I mean shouts and the level clips quite significantly, the rest of the clip from that point onwards is very quiet, until I remove the dynamics (cut it) and re apply it (paste it back) then it resets from that point onwards and it starts doing what it should until the next shout!

Is there anyother effect I can apply, I can't see why I can't just apply an effect and say boost the quiet bits to at least this level and limit the louder bits to this level (the original recording will obviously hopefully never clip, as I realise if it does theres nothing I can do about that)

Look forward to your advice and hopefully putting this long running issue to bed forever!

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Dennis RadekeRe: How do you combat fluctuating lav mic levels?
by on Nov 12, 2014 at 11:18:47 am

Wikipedia to the rescue!

Worth a good thorough read. If you've got full control of your dynamics processor, then I think that the knob you wish to tweek would be the threshold knob. This is the one that the defines the point at which the compressor/limiter kicks in.

Newer versions of Premiere Pro (maybe CS5?) also include the IzoTope Multiband compressor which is worth some time as well.

Hope this helps,
Dennis - Adobe guy

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David PayneRe: How do you combat fluctuating lav mic levels?
by on Nov 12, 2014 at 12:17:30 pm

Thank you Dennis. I'm going to have to spend some more time testing this effect as I thought I'd done all I needed to do to get the desired effect as described below. Here is a screengrab of my settings:

"The dynamics effect is a good way to fix problems with audio levels that vary too much. For example, if you have several people speaking and some of them are much quieter than others, it can be difficult and time-consuming to manually adjust the levels. Instead you can use this approach:

Lift the overall gain of the clip (or track) to a point where the quiet parts are loud enough.
The loudest parts will now be too loud, so add the dynamics effect.
Check the compression option and adjust the threshold and ratio until the louder parts are acceptable.
You may also need to enable the limiter option to safeguard against clipping."

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Jon HisemanRe: How do you combat fluctuating lav mic levels?
by on Nov 12, 2014 at 12:26:04 pm

It would seem your problem is with the release control on your compressor. I don't know the plug you are using but they all work in the same way except that some are inherently more transparent than others.
First check the ratio - 2:1 - 8:1 is compression - more than 10:1 and you are limiting.
Then set the threshold control - with some compressors you can set this to say -10db below your max signal strength and it will gently hold these loud sections. Then set the release control - this sets the rate at which the compressor will return to the non active state ready for the next high. For speech you can set this quite short, say 125ms. Adjust until the transition from the compressed audio to the quieter stuff is inauable as an effect..
Finally adjust the gain make up (if your plug has an output control) to make up for any loss in overall gain.
Remember that compressors are primarily for transparently decreasing the relationship between the quietist and loudest signals and should be used anywhere you want to narrow this gap.
I hope this helps

I used to be Jon Hiseman but I'm feeling better now.

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David PayneRe: How do you combat fluctuating lav mic levels?
by on Nov 12, 2014 at 3:50:37 pm

thank you so much John, I should have known it was lack of knowledge instead of lack of features causing this issue. I'll find a problem area of some dialogue and play around with this in depth tomorrow.

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David PayneRe: How do you combat fluctuating lav mic levels?
by on Nov 20, 2014 at 10:26:37 am

Thanks for the continued input guys. Sadly the mics I went for don't work too well at longer distance, they pick up way too much background sound.

I can't get my head around this compressor now, I've played around with all values but the fact remains, if I have limiter ticked, whatever i set the threshold and release to (the only 2 controls in the limiter) if somebody shouts and it peaks (or would have peaked if not limited) then the audio after this point is significantly quieter than it would have been if i'd not limited it...

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David PattersonRe: How do you combat fluctuating lav mic levels?
by on Nov 20, 2014 at 3:40:26 pm

If your limiter is limiting or compressing regardless of the threshold level, your input signal must be very hot. If you think the input level is normal, and your limiter only has threshold and release controls (no gain stage controls?), revisit the threshold control, as that control determines if and when the limiter will be activated. The settings may be counter intuitive, but just experiment with different settings while talking into the mic. As one extreme the limiter should not be active at all, and at the other extreme the limiter will kick in at even the slightest signal level. From what you've said, it appears that your threshold setting is causing the limiter to kick in prematurely.

The release control effects how long the signal remains compressed/limited after the initial transient. Long release times will keep the signal compressed, so start off with a short release time first.

Good luck.

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David PattersonRe: How do you combat fluctuating lav mic levels?
by on Nov 18, 2014 at 4:43:48 pm

You might consider placing your lav mic farther away from the person's mouth. If the lav is clipped to a lapel, the proximity change will be more drastic than if the lav was clipped lower (like around the sternum).

Compressors and limiters can do wonders, but expect to spend a bit of time learning how to use them without the audio sounding overly compressed. Heavy compression will bring out nasty artifacts, like sibilance and "pumping" of level changes.

For future recordings, you might try recording to two audio tracks; one at a normal level and one at a lower level. If someone speaks so loud they produce clipping, just fade that section of audio down and let the softer recording level replace it. This is a common recording trick for recording with unpredictable changes in volume.

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