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how birds make sounds



According to an article in the Nation & World section of the San Mateo
Times (from San Mateo, California) on 12/25/97, entitled "Researchers
discover how birds make sounds," birds do NOT generate sounds principally
from the stretched membranes within the syrinx, but rather it is the medial
and lateral labia that apparently regulate the air flow to facilitate the
birds' songs.  This was discovered when birds whose syringeal membranes
were removed in the laboratory were still able to vocalize "almost
normally."  Examination inside the syrinxes of unaltered birds with an
angioscope further revealed that the two labia move to close the air
passages as singing commences, but could not actually reveal the labia
vibrating, although the researchers expect that this vibration does occur.

The research was carried out by Franz Goller of Indiana University, and Ole
Larsen of Odense University in Denmark, and the study was published on
12/22/97 in the Proceedings of the National Academy of Science.

Goller stated that six muscles control each labium, and that the membranes
within the syrinx are just support structures, although they may add "some
control" to the voice."  Evan Balaban, an avian specialist at the
Neurosciences Institute in San Diego, likens the birds' syringeal labia,
coming together and moving apart from the syringeal wall to allow air to
squeeze through, to human vocal cords, which come together and move apart
to allow puffs of air to get through the larynx.

Would anyone care to comment on whether this new understanding of modern
avian sound production might (or might not) provide insight into the
vocalizations of  nonavian dinosaurs?

Ralph Miller III <gbabcock@best.com>