Sure, a recording system that has repeatable recording gain settings
(MDs with stepped record levels are ideal) can be used to extract the
sound pressure levels from your recordings.
You need to do a calibration--I use band-limited 200-2KHz pink noise,
and use a sound level meter to set that noise to 64dBA at the
selected spot in my studio.
Then I make a recording on my field outfit at the same spot, using a
known record gain setting. I use the "rms" mode of the "PAZ Meters"
plugin that come free with Pro Tools LE to get a dbFS reading from
the recording that corresponds to that record level.
A field recording made with a different gain can be calibrated by
knowing what the gain steps are. On my Sharp MD it's 2dB per step.
This all makes sense with omni mics. What the SPL is when observed
with a directional mic is questionable.
-Dan Dugan
p.s. I use 64dBA for my reference field because 1) it's 30dB below
the standard 94dB used to rate the sensitivity of mics, 2) It isn't
so loud it drives you crazy, and 3) a recorder set to around -5dbFS
recording level with a 64dBA field seems to be ideal for most
soundscapes.
-dD-
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