> Have a look at - http://www.daqarta.com/scrndx.htm

I was looking through the download sites last night and found some promising
material using the key 'audio analysis'.  Don't know what they can do and if
something could be built using one of them as a base.

Something that occurs to me is that most of us think in terms of the human sound
spectrum, effectively from about 20 Hz to 20,000 Hz (max). Acoustical vibrations
actually go right up into RF frequencies.  I am not sure if there is an upper
limit -- I'm sure there must be.

I do recall reading about a small superheterodyne device that would take the
band from 20K to 40K and transform it down to human range.  That was 40 years
ago, I would reckon.  It was a home project and used a mic for input and
earphones for output.  The unit was the size of a pocket transistor radio.

It claimed to put a whole new perspective on things like bird calls and insect
sounds. Things that were normally inaudible due to being above human pitch
became audible after transformation.  An apparently silent countryside would
suddenly become very noisy when donning the headphones.

That insects and birds make supersonic 'sounds' stands to reason, since the
vibrating parts of insects are very small and would be suited to higher
frequencies, rather than lower.

I think therefore, that it would be wise to consider a spectrum far wider than
normal human hearing for analysis.

allen