we may be making this way more complicated than it is.
perhaps defining the requirements a bit closer is in order
are you trying to pinpoint where some some noise is coming from?
have you considered a funnel, rolled up tube, long screwdriver with the handle to the ear? or stethoscope?
there are lots of directional microphones and computer programs that would allow you to run a virtual oscilloscope and select only certain wavelength/frequency.
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