Dear Barry,
During recent years, our lab has done some work in this
direction (as some collateral research). For instance, we
delivered a pilot report to the Fourth International
Conference on Bio-Acoustics, 10-12th April 2007, Holywell Park,
Loughborough University, UK (see below).
With best regards,
Eugene Kretchmar
Laboratory of Bioacoustic and Sensory Systems,
Faculty of Biology and Soil Sciences,
Saint-Petersburg State University,
Universitetskaya emb. 7/9,
Saint-Petersburg, 199034
RUSSIA
Abstract
THE POTENTIAL POSSIBILITIES OF THE LOCATING THAT GEESE USE
FOR SCANNING THE EARTH SURFACE DURING THEIR SEASONAL MIGRATIONS
Eugene A. Kretchmar, Alexey K. Makarov
The necessity of orientation in permanently alternating environment
is characteristic of long distance migrants. The basic tasks which
are permanently to be updated during the flight are the following
operational navigation parameters: flight direction, speed and
altitude; shape and features of ground surface; distances to
obstacles, etc.
The intensive acoustic signalling in migrating flocks under
conditions of limited visual orientation (i.e. night, clouds, fog)
may have not only communicative function but navigation as well. Thus
the larger Anseriformes like Greater White-fronted Goose (Anser
albifrons) or Middendorf Bean Goose (A. fabalis middendorfii) utter a
flight calls with characteristics being suitable for use them in
terms of navigation. The suitability of acoustic signals for active
sound spatial orientation (echolocation) depends on certain physical
parameters (Konstantinov & Makarov 1990). High amplitude and
frequency range of sounds determin effective location distance.
Signal shortness designates the minimum range of effective location.
The range of one-valued distance measurement depends on intervals
between the signals in a sequence. The steepness of leading and
trailing edges of signal amplitude determins resolution as of
location range.
The "flight squawks" calls having the frequency of energy peak
about 1 kHz (wave length 34 cm) which allow detecting the target of
1+ m in size are recorded in both mentioned species. When the
duration of separate calls of geese averaged 50 ms the skip distance
of location constitutes ca. 9 m with measurement error of flight
altitude < 4 m. The distance of one-valued location averages 17 m
with minimal interval between signals in a sequence being 90Б 100 ms
and would increased according with interval amplification.
Working range of such biosonar is determined by hearing ability and
echo-signal-to-noise ratio. The energy of echo-signal (Le-s) depends
on intensity of propagation (Lpr), air absorption loss (Lred) and
echo characteristics of located target (п t) and described by
expression: Le-s = Lpr - Lred - п t . The value of sound attenuation
with frequency of about 1 kHz is basically determined by divergence
of spherical wave front and constitutes 60 dB at a distance of 1 km.
The echo characteristics of located target depends on peculiarities
of located landscape and amount ca. 10Б 20 dB. Given the produced
signal has 90 dB of intensity, estimated threshold of reflected
signal value (10 dB above the noise level 20 dB) will be obtained at
a location range of 250Б 500 m. Increasing of emission intensity up
to 100 dB will amplify estimated location range to 1 km.
Thus, physical characteristics and background information on flight
calls in geese confirm prerequisites of their use for acoustic
spatial orientation by migrating geese. Hypothesis of optional
echo-location system seems to be viable taking into account known
facts of well developed echo-location systems in oilbird (Steatornis
caripensis) and Swiftlets (Collocalia salangana).
Monday, November 20, 2006, 8:26:07 PM, you wrote:
BB> For the last 5 years, I have been engaged in a research project exploring
BB> auditory spatial awareness in a wide variety of species and situations. The
BB> project has been published in my new book, "Spaces Speak, Are You Listening?
BB> Experiencing Aural Architecture," which MIT Press has just released.
BB> Fragmentary evidence in the literature suggests that there are many other
BB> species besides bats and dolphins that use the auditory sense to navigate a
BB> space, including shrews, rats, hamsters, and some species of birds. The
BB> problem for researchers is that they can only infer what an animal is doing
BB> by their behavior and that is extremely difficult to interpret. Humans also
BB> have the option to navigate and orientate in a space by listening, most
BB> notably some blind individuals.
BB> For those who have a chance to read the book, please let me know of other
BB> articles and research that would contribute to the foundation that I have
BB> created. My work is only a beginning.
BB> Additional information about the book can be found at the MIT Press web at:
BB> http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=10947 and I can
BB> provide copies of the Introduction and Table of Contents if you send me an
BB> email requesting them.
BB> Barry Blesser (former MIT Prof)
BB>
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