Asian elephants have a nasal pronunciation
University of Vienna / Phys. Org
August 23, 2022
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https://phys.org/news/2022-08-asian-elephants-nasal-pronunciation.html
for images.
With the help of an acoustic camera that visualizes sound pressure,
researchers from the University of Vienna investigated the calls of Asian
elephants. The elephants emitted their low frequency "rumbles" mainly
through their trunk or through their mouth and trunk simultaneously, and
only seldomly through their mouth alone. This is the first study to
conclusively demonstrate the combined oral and nasal call emission in a
non-human animal. The study has recently been published in the journal
Animals.
Elephants have the longest nasal elongation in the world. Not surprisingly,
their low-frequency, partially infrasonic rumbles resonate even deeper when
emitted through the long trunk. A team of cognitive biologists, Veronika
Beeck and Angela Stoeger, from the University of Vienna has now shown that
these vocal tract resonances, which is known as a nasal pronunciation in
human language, also play a crucial role in animal communication. The
researchers suggest that the increased vocal flexibility in Asian elephants
potentially allows them to encode more information. Also, the lower
frequency resonances may enhance the transmission of the calls over long
distances.
Humans form vowels though tongue positions, lips, and mouth aperture,
thereby shaping their vocal tract's resonances. Specifically, by opening
the velum and letting air stream through the oral and nasal cavities
simultaneously, humans "nasalize" the sound of vowels. In many languages,
such as French or Hindi, the nasalization of vowels changes the meaning of
a word, such as beau [bo] meaning "beautiful" in French and the nasalized
bon [bõ] meaning "good."
So far, mammals were expected to have far less flexibility to modify their
vocal tract (the oral and nasal pathways above the larynx) and hence on the
timbre of their calls. Across animals, calls often differ solely by being
emitted either through the mouth or nose. In this current study, the
Viennese researchers teamed up with engineers Gunnar Heilmann and Michael
Kerscher. Together, they pointed an acoustic camera at Asian elephants in
Nepal to see how they emit their calls. The acoustic camera, like a thermal
camera, displays sound pressure in color coding.
Calls were mostly uttered though the trunk. "To our surprise, the acoustic
camera also clearly showed calls that were emitted through the mouth and
nose simultaneously. The resonance spectra of these calls were very similar
to the ones described in human nasal vowels," explains Veronika Beeck.
Although this was suggested in fallow deer, elephant seals and Diana
monkeys before, this is the first study to conclusively prove orally and
nasally combined calls.
Based on this new evidence, the researchers suggest that mammal calls might
be more flexible than previously thought. Acoustic communication plays a
critical role in social systems, such as the complex matriarchy of
elephants, but the exact function of the mixed mouth–and–trunk emitted
calls remain to be investigated.
*More information: *Veronika C. Beeck et al, Sound Visualization
Demonstrates Velopharyngeal Coupling and Complex Spectral Variability in
Asian Elephants, Animals (2022).
DOI: 10.3390/ani12162119
*Provided by University of Vienna *
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