n calls
Because gibbons typically call from the canopy and live in a 3-D=A0
environment (as opposed to a plane), Rob, one would need to set up a=A0
tetrahedral (pyramid w/ all mics equidistant from one another) in=A0
order to approximate location. But because the rainforests where they=A0
reside (Sumatra and Borneo in my experience) are so reverberant, one=A0
would get complex arrival times at each mic obviating precise analysis=A0
of location. To further complicate matters, the acoustics of these=A0
biomes are in constant flux, changing rapidly with the slightest shift=A0
in temperature or humidity or time of day. That said, if one has taken=A0
careful measurements over time under different conditions, one might=A0
be be able to approximate both distance and location assuming well-
calibrated gear that one can rely on under those conditions.
Bernie
On Dec 17, 2008, at 8:20 AM, Rob Danielson wrote:
> At 7:51 PM -0500 12/16/08, Marc Myers wrote:
> >Anyone have experience locating animals by measuring distance and
> >direction of their calls in natural environments? Gibbons often live
> >in difficult terrain, at low densities and in small family groups.
> >They can be hard to see in their native environment and are
> >critically endangered through the majority of their range. Making
> >population estimates is important in conservation planning, when
> >advising local governments on forestry use and establishing risks to
> >extinction. Gibbons have famously loud and expressive calls,
> >typically sounded first thing in the morning. Populations are
> >presently estimated based on the frequency, direction and apparent
> >distance of the calls. Of course even experienced listeners are not
> >very good at estimating distance and as a consequence population
> >estimates vary wildly from environment to environment and researcher
> >to researcher. Any thoughts?
> >
> >
> >_
>
> Hi Marc--
> Here's another "wild" scheme. If pinpointing where the calls/animals
> are located is really important, one could record with 3 omni mics in
> a large, equilateral triangle layout. I'm not sure what distances
> between the mics to recommend but 500 feet or more would probably
> provide enough accuracy to identify their favorite calling spots in
> audible range with certainty, maybe even determine that animals are
> on the move. You'd need to know the exact distances between the mics
> and record all three tracks at once. Arrival time differences are
> easier to measure (and hear) with percussive calls than sustained
> ones and that might be an drawback with Gibbons. One could use
> wireless transmitters (a hit, quality-wise) but an option if running
> wire isn't possible. Rob D.
> --
>
>
>
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------------------------------------
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause
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