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Minor audio distortion – clipping or peaking not visible, but I hear it. Fixable?
Hi, I did an interview with a wireless lapel mic run through a JuicedLink pre-amp into a DSLR (Canon 7D). Thought I had everything set right, since audio levels appeared good in both camera and on the pre-amp, but discovered some minor distortion in post. (I did pull a test clip onto a laptop just before the shoot, but wrote off the “tinny-ness” as just the crappy internal computer speakers.)
In Premiere, the levels never peak into the red, and the waveform actually looks really good – no clipping or “flat tops” even in the louder parts. So I’m not sure why I’m hearing the distortion, especially during the louder inflections of the subject’s voice.
Not being very well-versed in audio, I experimented with a few filters, and the Lowpass helped the overall “tinny-ness” quite a bit. Is there much I can do beyond that for the louder bits where it’s more apparent? (Again, the levels never peak and the waveform doesn’t even appear clipped.)
Here are a couple pictures of the waveform (zoomed out/in), and the levels stay between -9 and -18.
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3 Replies
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You can experiment with reducing the gain 3-6dB and see if that takes care of it. But if the distortion is in the actual audio you can’t get rid of it… unless it’s very minor distortion in which case you can bring it into ProTools and draw out the peaks by hand. I think there’s even a plugin that can do that for you… again, only if it’s minor distortion.
Another thing you can do is put an EQ on that track. Select Mid3, narrow the Q and crank the gain so you are only listening to a very loud, but narrow band of a frequency. Then sweep through the frequencies to try and find the nastiest sounding distortion. Once you have located it bring down the gain of that frequency until it’s tolerable.
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If it’s not showing up in the waveforms, it’s likely the lav quality or perhaps it’s malfuncting if it’s a good manufacturer. How much did you pay for this mic? I tried an Azden lav once and it was terrible. Harsh as heck. I threw it out. The 7D should be fine, as long as you didn’t overdrive it (which it appears you didn’t). The JL should be fine also. Try the EQ stuff mentioned by Dave.
Al
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Thanks Dave. I don’t have (or would no how to use) ProTools, though it does seem pretty minor which is what made me hopeful enough to post here.
In Premiere I tried putting the EQ on a track and following your instructions, which did help a little. Thanks! I know enough to know that there’s not much beyond “a little” that can be done in post with distortion. I think it’s definitely tolerable and minor enough to not be distracting at this point.
Al, I was using a Sennheiser lapel mic kit, which has always performed wonderfully, and actually just recently had the little mic itself replaced. Had to be something in the pre-amp I’m thinking. Will run some more tests before the next shoot.
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