> Fernando Gonz=C3=A1lez Garc=C3=ADa wrote:
> need(s) to buy a recorder and a microphone to record
> the sound of the wing=C2=B4s movement of insects to
> measure the cycles per second of the each wing
> movement.
Having done this with Drosophila back in the early
70s, I would recommend that the best technique is to
put the microphone very close to the insect. In my
case, I built a collection jar where the bottom of the
jar WAS a microphone. That gave me very good
acoustical gain. Doing that may not work for your
friend, depending on whether or not he is recording
insects that he has collected or if they are in the
wild.
In the wild, I would try stringing several lavaliere
type microphones in whatever flora where the insects
congregate. If the insects fly near the microphones
then he should be able to get a good recording.
Obviously things will work better with a sensitive,
low-noise microphone, but being close is much more
important.
I have one further idea. That would be to use an
elliptic microphone. If you think of a parabolic
microphone as being one that is focused at infinity,
and therefore excels at recording distant sound
sources, the elliptic microphone has two focii, one
where the microphone capsule is and another some
distance away. It should be possible to build
elliptic microphones with a focal length of 1 meter or
so. Basically, almost all of the acoustic energy
emitted by the insect, located at the second focus,
would be captured by the microphone capsule, located
at the first focus. So far as I know there is NO
literature on this type of microphone. But I have
done some analysis and would be happy to collaborate
on construction of such a device.
I hope this helps.
Eric Benjamin
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