Hello David,
I'm curious to learn whether the concept of fetch might have something to
do with the steepness of the transfer function of a given microphone. Yes,
typically we only get one number for that at a 94 dBSPL test figure, but it
doesn't follow that the mV/Pa is a linear function over varying pressures, =
*
or* that the slopes of I/O for any 2 microphones with the same 94dB
sensitivity figure are the same.
Let's say we have our scene with a distant source of particular interest
producing say, 10dBSPL less than some other nearer source.
Now, let's assume for this purpose, we have 2 gun mics with the same polar
pattern and the transfer functions are both linear but have different
slopes. #1 has a sensitivity of 20mV/Pa, #2 is 10mV/Pa, - I'm guessing #1
likely has a steeper TF slope than #2. Both have a sufficiently low
self-noise to be used for nature work and our mic pre's are near
noiseless, at the gains applied. We adjust gains so that both mics are
reading the same max dB value.
I'm thinking the less sensitive mic will do a better job of 'fetching' the
more distant sound since the difference between the source-of-interest's
output voltage and that of the near sound will be less. In effect, the
lower sensitivity mic is compressing the sonic scene or, after a more
rigorous examination, the higher sensitivity mic might be expanding it.
This thought also has me wondering if a compressor is a flexible fetch
control, suitable for nature work and what the group's opinions are
regarding the use of compression/expansion in nature recording.
thanks!
Keith
On Thu, Mar 14, 2013 at 3:22 AM, Raimund <>wrot=
e:
> **
>
>
> > > http://www.avisoft.com/sounds/bsp4.mp3
> >
> > Raimund,
> >
> > That's a great recording, You can hear the whole tree resonating.
> >
> > (Now with technical hat on)
> >
> > I looked for Sennheiser HF noise on a power spectrum. This is a
> > characteristic tip-up above 10KHz due to thermal noise which is as low
> > as you can get. The mic hiss just below this frequency is about 55dB
> > below the unfiltered background noise and about 80dB below the
> > woodpecker. That is some going by a large margin.
> >
> > With a cheaper mic and 10dB more noise, that mic noise would be still
> > below audible limits. This suggests that for much of our time, good
> > technique beats mic specs by a large margin and we can get too hung up
> > on manufacturer's figures instead of just getting out recording. I
> > will have to be content with my MKH-416's 13dB(A) noise figure. :-)
>
> Hi David,
>
> Yes, that woopecker was really close to the mic (if I remember correctly
> it was only about two or three meters).
>
> Unfortunately, we often don't manage to get that close. Most of the time
> the distances are considerably larger. Under these (more common)
> cirmunstances I can almost always hear the difference between my K6/ME66
> (10 dBA) and the MKH60 (8 dBA) even in relatively noisy environments.
>
> Regards,
> Raimund
>
>
>
--
Keith Smith
Keith Smith Trio, Northern Lights =96 Altai Khangai - www.keithsmith.ca
Photography - www.mymountains.ca
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