Maxim suggested that sound generated by bats is reflected
from obstacles, and is detected by the bat on its
return. The bats gets enough information from these
reflections to work out where obstacles are, and to
avoid them. This is actually more or less how biosonar
works. However, Maxim got the source of the sound
and the organs the bats uses to detect the sound completely
wrong!
According to Maxim, bats generate very low frequency sounds with the
beating of their wings. As their wings beat at perhaps 5 to 20 times a
second, then they would produce sounds at a frequency of 5 - 20 Hertz
(Hz, cycles per second). This frequency is too low for human ears to detect
(we now call it 'infrasound'), which is why, Maxim thought, we are unaware
of the sounds they produce.
When the echoes from this infrasound returns to
the bat, Maxim thought they would detect it with touch
receptors on their wings and their facial appendages
(like Braineville's bat, page
1).
If only Maxim had combined his idea with the knowledge
that bats use their EARS for obstacle avoidance (gained
by Spallanzani, Jurine and Hahn), he would have found
the answer!
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