It is the downward stroke of a bird’s
wing that generates sound. That sound
does not travel any measurable distance, as disruptive air flow immediately dissipates
the waves. Normal sound waves travel
easily through the atmosphere without any distortion from the wind, therefore,
it is this difference between normal sound waves and those made by a flying
bird that resulted in the University of California, Berkley setting up a
laboratory to study the difference.
The various birds studied were
crows, seagulls, hawks, owls, blue jays and sparrows. Sound recordings were made in a controlled environment,
over a three-year period.
On several occasions the work had
to be stopped as the hawks and owls kept eating the sparrows.
Funding was eventually pulled.
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