>the least expensive way to accomplish that would probably be to use
>an Avisoft Bioacoustics phantom-powered electret ultrasound
>microphone (http://www.avisoft.com/usg/ep3.htm) in conjunction with a
>cost-effective 192 kHz USB audio interface such as the E-MU Tracker
>Pre
>(http://www.emu.com/products/product.asp?product=17511&nav=features).
>The microphone would cost $550 and the audio interface about $150.
Raimund,
I notice the Avisoft mics use Knowles capsules and I've tried several
of these with some success up to 120KHz. They need a little
equalisation and this brings up the hiss above 80 KHz. I've tried to
minimise this with a home designed impedance matching preamp but that
experimatation has stagnated a bit looking for the ideal op-amp.
Several commercial bat detectors use Knowles capsules, but they also
tend to be hissy, but if that is not a problem Knowles may the
affordable solution to recording ultrasound. They use the same circuit
as any other electret capsule.
I can't find a freqency spec for the E-MU products and I fear that as
audio devices, they may well limit the bandwodth to avoid problems
within the audio region. The last thing you need in any audio setup is
interference from a source you can't hear. Digital buses can be a
nightmare. 192s/sec gives a much cleaner audio top end, but not
necessarily a higher frequency range. If anyone knows otherwise, I'd
be interested for bat work.
The reason I was discusssing downshifting the ultrasound frequencies
for analysis is that audio software seems to be much more affordable
than specialist ultrasound analysis. Someone please prove me wrong.
:-)
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
|