Steve Jacobson's observation that it is difficult to localize the
chirp of a cricket, because the echoes are so loud and numerous
that you cant tell the sound source from the ricocheting racket,
or something like that, precipitated some loud research here at
headquarters. You see, I collect whistles. Don't know why.
Always have. I have a drawer full of whistles ranging in size
from a peanut to a football. Then just for good measure, I have
a few sirens, clickers and mechanical birdcalls. So, naturally,
when Steve tripped my wire, I headed for the whistle drawer and
started tooting around the house and yard.
After eliminating the foghorn and train whistles, steam and
diesel types, I settled down to the task of finding whistle, when
caused to emit a short blast, delivered the most echoes. The one
I like best is a adjustable dog whistle tuned to it's lowest
pitch, which turned out to be right on high G. note 83 on my
Yamaha grand piano, or any other piano that is tuned to standard
pitch. The frequency of this note is 3136 vibrations per second.
A long time ago, I had a friend who was a girl that boasted
perfect pitch. Once when we were sitting in the grass listing to
a cricket advertise for a mate, I asked what is the pitch of its
chirp. She was certain that it had two components--B and C. I
asked, what octave B and C, and got no reply.
Back to my dog whistle. To produce the best possible sound, blow
as hard as possible, for the shortest possible time, so as to get
a high energy beep. A really loud beep will rebound from all of
the surfaces in the environment long enough to be heard after the
whistle has stopped sounding.
If you don't have an adjustable dog, I suggest you try the
experiment with the littlest key chain whistle you can find. And
if you don't have a little key chain, you might try blowing over
an empty 22 caliber cartridge.
The actual pitch produced by the whistle does not have to be high
G. But, it does have to be somewhere on the Fletcher-Munson
curve.
I suspect that a glissando that sweeps across the crest of your
audiograph curve would be best for you.
The bat, and a few other creatures of nature, have exquisite
navigational systems based on supersonic echoes resulting from
chirps that sweep somewhere in the neighborhood of 60 to 90
kilohertz. Using echo sensing, bats have been observed catching
meal worms tossed into the air. They clearly detect everything
of interest to bats by just listening to reflections of their
emitted sounds. Some researchers posit that they have a
mechanism for blocking their hearing during the period while they
are generating their chirps, thus avoiding masking the returning
echoes.
I don't think this blanking trick is a learned skill. Since you
and I cant turn a deaf ear to our own beeping, an alternative
might be to cause the sounds to originate from somewhere behind
us. You guys got any ideas?
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