I'll chime in to support of Gianni's broader acoustic context plea. What we=
understand about animal acoustic communication has to a large degree been
determined by sampling with transducers/microphones designed for the
frequency range of human hearing. Borrowing a newly developed ultrasound
sensor from someone in a physic department, let Don Griffin (re-) discover=
bat ultrasound in the 1940's. The exploration phase in both animal ultrasou=
nd
and infrasound is still in an early stage (i.e., what animals use these
frequencies?).
Another recent paper demonstrated ultrasonic alarm calls in squirrels. The=
idea is these are highly directional and may be inaudible to the predators.
Yet another shows ultrasonic harmonics in both frog and bird calls.
Whether the ultrasonic components are epiphenomena or have a communication=
function in different animals or settings will keep interested folks busy f=
or
some time to come.
The cost of specialist microphones and recording gear has been continuing=
barrier to more general investigation outside the human hearing range for
professionals and natural history enthusiasts alike.
Relatively inexpensive portable high sampling rate consumer Ato D interface=
s
or digital recorders suggest this sort of investigation is now more afforda=
ble
(assuming a suitable microphone), but, as Gianni and Raimund have shown her=
e,
the antialiasing in the devices they've tested is, unfortunately, designed =
for
audio range input.
Bill R.
=3D=3D=3D=3D=3D
Narins, P. M. et al. 2004. Old World frog and bird vocalizations contain
prominent ultrasonic harmonics. Journal of the Acoustical Society of Americ=
a
115:910-913.
Wilson, D. R. and J. F. Hare 2004. Ground squirrel uses ultrasonic alarms.=
Nature (London) 430: 523
Sun, J. W. C. and P. M. Narins 2005. Anthropogenic sounds differentially af=
fect
amphibian call rate. Biological Conservation 121:419-427.
=3D=3D=3D=3D=3D=3D=3D=3D
=3D=3D=3D=3D=3D
> Hi Gianni,
>
> I agree with your thoughts.
>
> Those who are interested in such ultrasonic communication signals
> might visit the following pages:
>
> http://www.avisoft.com/sounds.htm#insects
> http://www.avisoft.com/sounds.htm#bats
> http://www.avisoft.com/rats.htm#samples
>
> The recently published scientific paper on the ultrasonic songs of
> mice is available here:
>
> http://tinyurl.com/7s3te
>
> Regards,
> Raimund
>
>
> Gianni Pavan wrote:
>
> > I would now consider a different point of view. Recording at high
> > sample rates is important for studying sounds used by animals to
> > communicate and to echolocate.
> ...
> > A further motivation for extending the bandwidth is to have
> control
> > on the whole acoustic context. In studies about communication in
> > mices it has been discovered that other than audible sounds,
> > ultrasonic sounds up to 90 kHz are used for communication.
> ...
>
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