Hi Barry, 

>  Chris was mentioning about a way to make seismic files audible. How did
> you do it?  Was the voltage to frequency a product function?

I used the digital data in a typical "PSN" file. Its easy to do,
just remove the header, replace it with the "wave" header and fill
data segment with the PSN data (short).

To make the sound audible just play back the PSN file at a higher rate.
Say, a 10 minute file (600  seconds ) with a sample rate of 50 samples 
per second would be played back as follows.
  Maximum upper frequency you require is say 4000 hertz.
  Samples per second = 50

   600 / (4000 / 50) = 7.5

thus the 600 second file will be played back in 7.5 seconds. the data
in the audio file is identical to the PSN data.

If you want, download the program "Recent" from my web site and convert
a few files. About two years ago a chap, converted a months worth of
seismic data and converted it to audio. He sold it, on a CD, with all
sorts of unusual sounds. It was interesting to hear a large overseas 
quake followed by the reflections from the earths core.

The site is : http://members.iinet.net.au/~ajbv/

Cheers

Arie

>    Chris was mentioning about a way to make seismic files audible. How did
> you do it?  Was the voltage to frequency a product function?
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