pers
Hi there,
This IS geting intresting. I am going to assume that you guys are now
using some form of digital decording medium. Is there any chance that
the process of analog to digital, then in the case of mini-disc,
compression and later de-compression, and the digital to analog
conversion so that we can listen to the signal again, would introduce
some sort of minute distortions? Is it also possible that the Mini-
disc compression leaves out something vital because it "thinks"
that "this little bit is not needed"?
I guess I am old fassioned but sometimes it takes me a while to
completely trust new technology.
Still learning,
Dennis
--- In Walter Knapp <> wrote:
> Randolph S. Little wrote:
> > NatureRecordists:
> >
> > Hope I'm not the only one who is finding this thread to be quite
productive;
> > if so, please advise and I'll not pursue it further on this forum.
> >
> > Walter Knapp's latest reply finally sparked what I think is a
highly likely
> > hypothesis. Whereas, with a single sound source something like
multi-
> > pathing can create the reported effects (e.g., ghosts on a TV
image), if
> > there are multiple sources at similar frequencies then the
effects of
> > constructive/destructive summation are inevitable (e.g., beats
between
> > engines on any multi-engine aircraft). No non-linearity is
required. This
> > is a simple consequence of convergence of multiple acoustic waves,
> > and affects the instantaneous sound pressure level at the
microphone
> > just as at our ears. And the effect is not amplitude dependent
in the
> > sense that overload distortions are.
> >
> > This multi-source interference is not often encountered in any
birds that
> > I have typically recorded, but it is certainly a fact of acoustic
life in
> > many
> > other situations such as vocalizing choruses of insects and
amphibs.
> >
> > Mea culpa; I should have thought of this hypothesis much sooner.
>
> I was thinking about this last night. Frog recordists are very
likely to
> encounter this frequently as frogs are almost always group callers.
For
> us it's so routine we generally don't even think about it. You
really
> notice it when you are sifting your recordings for clean calls for
a ID
> clip for the species. As I happen to be doing right now.
>
> But bird recordists mostly record single individuals calling. This
would
> not occur there, at least not this particular thing. And on top of
that,
> not many birdcalls are long drawn out things of a single frequency
where
> this is easiest to hear.
>
> It does occur in insects in my experience where you have enough of
the
> same species calling simultaneously.
>
> With the frogs, particularly the toads, I'm speculating it's not
just a
> accidental thing, but a contrived arms race in the battle to get
the
> female. I've found that frogs are highly aware of their acoustic
> environment. Their calling locations and how they call give every
> evidence of careful choice to maximize their chances. It's probably
> mostly hard wired into them rather than thinking like we might do.
With
> most species the optimum acoustic locations are fought over. Which
is a
> whole different set of calls as that's got a vocal component too.
>
> I've spent many nights listening to and observing gray treefrogs
> jockying for optimum location around the rim of a half cask water
garden
> they like on our front patio. Some locations along the rim the call
> carries farther, and those spots are fought over all through the
evening.
>
> Walt
>
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