50kHz pitch shifter

[Curtin, Steven D (Steven)]

I heard a report on NPR where they were closing a former mine in Colorado
that was now a home for bats.  They had devices for detecting the bats that
pitch-shifted the bat's "radar" signal into one we could hear.  Here's some
info I found on this device after a quick search.  This would be interesting
for hearing other sounds out of the range of human hearing possibly.   My
guess is it uses heterdyning circuitry like the Theremin does to transpose
the pitches into our hearing range.

http://www.batcon.org/seedark.html#one

> ----------
> From: 	Martin Czech[SMTP:czech at Micronas.Com]
> Reply To: 	Martin Czech
> Sent: 	Tuesday, June 13, 2000 3:39 AM
> To: 	tpaddock at seanet.com
> Cc: 	synth-diy at node12b53.a2000.nl
> Subject: 	Re: 50kHz pitch shifter
> 
> A related question:
> 
> When astronomers started observation out of the visible band of light
> (ie, infra red, radio, gamma etc.) they detected a whole new universe.
> 
> Now, would that be true for sub and super sonic?
> 
> It would be interesting to hear, what super sonic noise is on the
> streets...
> 
> I've heard of people recording sub sonic phenomena (water level of a lake)
> and play that back with higher speed. This is no problem, but some kind
> of DC sampling device is needed (most audio ADC are sigma-delta and have
> a zero at DC...)
> 
> And I've heard about people recording bats. Now , tape recorders are made
> for the audio band, they will not work. Same applies for most sampling 
> technology. Frequency shifting will destroy harmonic relationships.
> 
> Any ideas?
> 
>