> My SD 702 allows for the Tone Level to be set. Is there an
> advantage with a particular level, and what benifit do we get by
> using a know level?
A tone generated in the recorder is useful when making a transfer of
the recordings to an analog medium. This is rarely done any more. It's
also useful (and often required) in a network or studio production
situation as a clear indicator to the next handler of the material
what your mixing reference level was. That has little application to
nature recording, unless you're Martyn and submitting it to the BBC.
A recorder-generated tone tells you nothing about the actual SPLs of
what you were recording. To do that you need a microphone calibrator,
which only works with omni mics and usually only has adaptors for
popular measurement mic sizes. I have one, but I'd have to pay a shop
to machine an adaptor for my 3032s, and its 94 dB tone is too loud for
the gain settings I use.
It's useful to have some means for calibrating your mic/recorder
system to a known SPL if you're doing any kind of bioacoustic science,
and/or if you're recording interfering anthropogenic sounds and want
the recordings to provide evidence. Calibration means scientific and
legal value.
I'd like to develop a field calibrator that would work with the kinds
of mics we use, and with windscreens. My current concept would look
like a little bullhorn with a transistor radio antenna coming out of
the front of it. Pull out the antenna all the way and you're at one-
half meter from the mic when you touch the tip of the antenna to the
windscreen. Pull the trigger and deliver, say, 64 dBA to the mic head.
Given the wonders of cheap electronics, it wouldn't be difficult to
follow the tone with a data burst that would carry GPS and weather
data, and/or a robot voice announcement of same. Now in post balancing
multiple channels would be a snap, and recordings could be self-
documenting.
To return to your original question, the normal "0 VU" level for
digitally acquired material is -20 or -18 dBFS, and you'll find -20 is
the default setting on your 702.
|