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Re: Preventing Thunder Distortion

Subject: Re: Preventing Thunder Distortion
From: "Bruce Wilson" bruceumba
Date: Mon Jul 17, 2006 10:02 am (PDT)
I had a similar experience when recording train whistle blasts from close
up. Since I had the gain turned down to a minimum, and the mic pads at -10
dB I thought I could record without wind protection. I confirmed this was a
good setup by listening to the mics when no train was around, and it sounded
very quiet when the bass rolloff was on.

When the train came by the whistle distorted badly, and turned off and on
during as single blast. Turns out I was so near the maxumum diaphram
excursions from the whistle levels (I was using large-diaphram mics), that
the addidion of wind pressures drove it into a very non-linear region.. When
I put the wind cover on for the next train the whistle sounded fine.

So now when I want a very loud sound I turn off any bass rolloff so I can
sense when wind will affect my max SPL.

Bruce Wilson
-----Original Message-----
 On Behalf Of guyhand2
Sent: Monday, July 17, 2006 7:26 AM
Subject: [Nature Recordists] Preventing Thunder Distortion

I've been familiarizing myself with my new Sound Devices 722 and Shure VP88
stereo mic by recording the numerous thunderstorms that have rumbled through
Idaho this summer.  
Although I've been careful to keep my volume levels low enough not to
distort the loudest cracks of thunder, I find the occasional sound of
distortion in playback.

When I look at the waveforms in ProTools, I don't see any clipping and they
appear to be well below a distored level, yet I can hear it now and then
(but not on all of the thunder, and not neccessarily on the loudest

Do I need to change the Gain Range on the 722 from "normal" to "low" even
though the overall level is lower than I'd like?  Any other suggestions?

Also, on a slightly different slant on sound levels,  I find that in general
recording on any of my mics if I don't keep the volume near the top end of
the level meter LEDs on the 722  (near the 0 dBFS mark), I get a far more
anemic final level (as seen in a ProTools wave form) than I was accustomed
to getting on my old Sony DAT recorder at what appeared to be more moderate
levels.  Any suggestion?


"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg 
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