Bat Sounds & Phonology

I have an idea for a race of creatures that evolved from bats instead of
protosimians and I'd like to give them a realistic language.  The only
problem is, I can't find any real sounds of bats that haven't been
electronically altered!  So, what kinds of phonemes do you all suppose
they might use?  (I'd prefer to keep this in the human audible range,
though, so don't get too crazy!)
Also, if anyone has any idea where I can find actual bat sounds on the
Internet, I'd love to get it.  Especially *free* resources!

Thanks,
Jim
--
"It's better to light one candle
   than to curse the darkness."
-Chinese Proverb and The Motto of the Christophers
                      http://www.christophers.org

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