Roger, in Bangkok wrote:

> I expect their problem is with connectors and seals, and they have
> asked for help to locate and correct the problem.  Seems simple enough
> to sniff around with a tiny microphone.

  I seem to recall that one approach to tiny air leaks is to consider
that the wavelengths of sound emitted are likely to be comparable to the
size of the defects.  This suggests that you might look for *ultrasonic*
frequencies for starters.

  Two advantages of looking for ultrasonics are that there is less
ambient noise and most ultrasonic detectors are *very* directional.
--
  Cheers,
        Paul B.