At 11:50 AM +0000 3/19/09, biv0uac61 wrote:
>Hi all,
>
>My current setup is a SD302 to a PCM-d50 and using a Sennheiser
>MKH-418s or Rode NT-1. My question is:
>
>When recording quiet ambient landscapes, what would be the best way
>(or your own method) to set the levels for this using the 302s gain
>and fader?
>
>The area is so quiet that it barely registers on the 302 meters and
>if i turn the fader or gain up a bit i start getting noticeable
>noise from the preamps. Any suggestions?
>
>Thanks!
>
>Terence
>
Hi Terence,
There is a practical limit as to how far you can "back-off" on the
gain without quality loss and Michael's and Philip's suggestions seem
to be consistent with this limit and your gear.
I find that I need about 60 dB of pre gain to record minimal
nocturnal presence in a rural location with a mic that has 16 mV/Pa
sensitivity. With the 302 and the mics you provide, you'll probably
have a little more gain available to you than you'll need for most
situations.
I use a simple method to see whether that the "saturation" level of
your background sounds is above the limit. This insures that I'll be
able to discern details in the far-most, quietest sounds in my
recording and maximize "headroom" for louder sounds that happen.
Open your field recording in a waveform editor like Audacity and find
a section where the amplitude (the vertical height or width of the
waveform) is the thinnest, the quietest. Make a 5-20 second extract
of just this section and open this extract in a waveform editor.
Select all of it. Use the "Find Peak" function of your editor to
determine what the "saturation level" is of this quietest moment.
(Sometimes, this info is provided in the Gain Change window). If the
reading is at least -55 dBFS (most waveform editors use a 96dB
scale), there will be no quality loss due to quantization noise on a
16 bit recording. If the number is smaller (a higher value,
_negative_ number like, "-60dB"), then you need to use more gain with
the 302. If you record in 24 bit mode, the file saturation can be
somewhat lower, but I would not lower the saturation unless I was
trying to record very loud sounds at the same time.
Here's a field test I ran with examples if you are curious.
http://www.uwm.edu/~type/audio-reports/LowSaturation/LowFieldSaturation2.ht=
ml
Rob D.
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