Our research projects with the NPS and the USFWS have shown promise in
this area.
Because we're often recording in areas where noise is intermittent
(aircraft, land-based vehicles and other non-biological sources) and
where we're capturing long clips, we have been able to derive some
good data on what happens to the entire biophony (including birds,
insects, amphibians, and even, occasionally, mammals) when noise
begins to mask the biosources present in the natural soundscape.
That's because we can show what is occurring up to the point where
noise intrudes enough to have an effect, what happens during the most
intrusive moments, and what happens after the noise has dissipated and
the biophony begins to recover. One of this issues is that we haven't
been able to resolve is the myriad complex ways in which different
types of noise affect different species. I. e., a prop plane vs jet vs
helicopter. A truck vs straight-piping motorcycle. Etc. Etc. But we do
have some general data on that issue that can be shown in spectrogram
series (before-during-after).
Bernie
On Mar 13, 2009, at 11:21 AM, saspring2002 wrote:
> --- In Rob Danielson <>
> wrote:
> >
> > At 3:48 PM +0000 3/13/09, Raimund Specht wrote:
> > >--- In
> > ><naturerecordists%40yahoogroups.com>=
s.com
> ,
> > >Rob Danielson <type@> 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.
> >
> >
> > --
> >
> >
> Rob I think your idea of recording the background noise in sync with
> the bird song is an interesting concept. For the purposes of my
> study I will most likely be recording the ambient noise directly
> before and after the bird song is recorded in order to get a general
> idea of the overall noise level of the area. In the end I am hoping
> to determine that Phoebes alter their song, whether it is time of
> day, duration, frequency, etc. in response to urban noise. I will be
> comparing Phoebes found in rural locations vs. those found in
> several urban parks. I think simultaneous recording would be the
> next step to take if I found an alteration in the song and I wanted
> to discover more about the response of the bird song to specific
> urban noises. I just wanted to thank you all again for getting
> involved and helping me through some of the more technical aspects
> of my project. I am enjoying the back and forth of ideas as it is
> helping me to think of the nearly limitless directions I could pursue.
>
> Travis
>
>
>
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