Randolph S. Little wrote:
> NatureRecordists:
>
> I trust we all know that harmonics of any single fundamental, as well
> as sum and difference frequencies of any multiple fundamentals, are
> the inescapable effect of any nonlinearity in any medium through which
> such signals pass. This includes not only the natural environment, but
> also the human hearing system, the sound recording system, the sound
> playback system and the sound analysis system. OK?
The one that seems most forgotten is the natural environment. We have
decided that certain types of sound are a error, and think accordingly.
The last thing considered seems to be the one that it's the natural
sound. That should be the first question.
> Given that, has it occurred to others that "seeing" a possible distortion
> product in an audiospectrogram and "hearing" the same component
> in the field is no more proof that the source created the component
> than it is proof that the recorder did not create an instance of it?
>
> It may be naive to claim perfection in recording equipment based on
> human hearing, particularly when the recording is of a non-human signal
> which has evolved via non-human perceptions.
There is always Occam's Razor. I say that proposing a system requiring
two or more simultaneous errors to have exactly the same result is less
likely to be correct than that there is no error. The simple explanation
there is that it's as we hear it or record it.
I'm well aware that recording equipment is not perfect. In this case,
what I hear in the wild, what I hear in the recording are the same, and
agree with the sonogram. If you have a method where such detailed
perfection of multiple error is proven, I might believe it. But it's
certainly a far more complex hypothesis. Not just one error, but multiples.
On top of that, most all the proposed errors require that the recorder
or some other part of the system be driven with a high signal level. But
this records at a low signal level as well, where those errors would not
occur. And the hearing errors that occur at loud calling also don't
apply as we can hear this at low levels too.
And on top of that, the "error" turns on and off with the 2nd toad. The
exact instant one toad gets it to himself, the sound is smooth and clear
(at least for American Toads, which have a pretty musical trill). Keep
in mind that the 2nd toad's call may be distant and weak, while the
first toad is right at you and very strong. So these errors come and go
with the calls, does the toad throw a error switch?
And note that I even can find a competitive reason why frogcalls should
be like this. A hypothesis at this point. You can't outshout your
competition, but you certainly can disrupt the signal so the female will
have a hard time homing in on it. It does, in fact, take less energy
than outshouting. Then all you have to be is persistent enough to get
your call out unobstructed. Burn half as much energy as your opponent
(which is enough) and you will outlast him. The toads are expending
considerable energy on this. I'm pretty sure that's what the long
trillers like toads are up to. Other frogs are more "civilized" and will
try to separate their calls, or their attraction system is different.
Next part is for someone to examine the reactions of the females. We may
find it works this way with long trillers, but the others it's a case of
some aspect of the formation of the call that attracts the female.
On top of that a frog that's calling has the problem of being located
and eaten. Disrupting localization has survival value there too. I
believe it was Bernie who related how disruption of calling patterns
lead to increased predation. The toads I'm talking about are calling
right at the water's edge, in very shallow water, not up in anything, in
the open in plain sight. Easy pickings if they can be found.
Walt
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