At 3:48 PM +0000 3/13/09, Raimund Specht wrote:
>--- In
><naturerecordists%40yahoogroups.com>=
m,
>Rob Danielson <> wrote:
>
>> Hi Raimund--
>> I'm still wondering what folks are proposing to sufficiently document
>> the back ground sounds as they appear to be the primary variable in
>> his study. If directional mics are needed to gain the 6-10dB of extra
>> separation from other, ongoing HF sounds, perhaps Steve's idea of a 4
>> channel recorder is a good route for Travis to pursue. I have been
>> reading good things and hearing some impressive files generated with
>> the Edirol R-4 Pro, but I think even the R-44 pre's have been
>> upgraded since the initial release. Rob D.
>>
>
>Hi Rob,
>
>I'm not sure whether it is required to record the background noise
>simultaneously. I guess that the background noise is in most cases
>more or less stationary so that it would be sufficient to take a
>short sample before or after recording the individual bird songs. If
>that was not sufficient, I think that one could still use a common
>stereo recorder. Another strategy might be to use just a single
>(calibrated) omnidirectional microphone for both. If the distance
>between the microphone and the singing bird is not too long, the
>spectrographic analysis of the bird song might still work reliably
>enough.
>
>Regards,
>Raimund
>
Hi Raimund--
Isn't it true with most animals that background sounds are most
distractive when changing in volume and/or pitch? I also wouldn't
rule out low frequency impacts because stress can reduce the amount
of singling, not just the song. I don't know if its the surroundings
here in SW Wisconsin, but I often find/see Phoebe nests tucked into
structures with lots of mass-- concrete silos, stone walls, just
inside caves and brick buildings. In the examples that come to mind,
the nests were positioned so that road sounds were partially abated.
I would definitely opt for recordings that would allow me to study
the background dynamics in sync.
In the city at distance of a few blocks from roads the background
levels might become reasonably steady above 100 Hz. In no locations
are background sound levels consistent under 40 Hz because these
sounds come from great distance. And, of course you'd want to be to
track the dynamics of the background sounds that are masking the
speech bandwidths of which there are many. I'd want a stereo
recording because-- during and after the fact-- when I can tell where
a sound is coming from, its identification is much more certain. I
have little trouble localizing sounds at 80Hz with a capable stereo
array, including binaural.
The only trouble I have making clear sonograms out of recordings made
with ambient rigs is when two or more callers are going at once. Its
hit and miss on the location of the intruding caller(s) even with a
shotgun. With two omni's in an ambient rig, you get spatial imaging
and the ability to use either channel for sonograms. Rob D.
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