about 24 kHz is the frequency whose half-wavelength is 7mm. theoretically
this is the max frequency for which we get a single frontal lobe and sounds
at 90 degrees are canceled. at increasing incoming frequencies multiple
lobe appear.
Gianni
2014-10-15 19:11 GMT+02:00 [naturerecordists] <
>:
>
>
> > II was wondering that as well.
>
> Yes the aim is to have a very narrow cone
>
> >I have experimented with a parabolic reflector for bat detectors. It gav=
e
> directionality but the gain was not
> helpful as aiming the rig was difficult because the bats were too mobile
> to
> follow.
>
> yes it's right I've done a parabolic microphone too with an ultrasonic
> sensor but it's very hard to follow bats while it's easier to listen the
> bird song with an audio parabolic microphone
>
> >There was an increase in gain, but in practice the absorption of
> ultrasound in air is the dominant effect on range. The limit for bat
> detectors with Lesser Horseshoe bats is about 5 to 8 metres after which .=
..
>
> regarding the amplification it's necessary to use a precision operational
> amplifier, the problem to keep the SNR at a good level. The distance is
> completely relative ... to so many factors!
>
> >The array spacing appears about the same order as the wavelength at
> 40KHz.
>
> it's 7 mm so about 24 khz
>
> Ivano
>
>
>
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