Whirlpool Refrigerator

My 2002 side-by-side Whirlpool refrigerator makes an intermittent chirping sound. This occurs :30 - :60 seconds after the fan kicks on (to start cooling).
- I'm assuming the problem is not associated with the compressor since I'm not having a problem with cooling. Is this correct?
- The sound doesn't seem to come from the ice maker.
- The other two moving parts are the condenser fan and the evaporator fan.
I've opened the freezer door and the sound doesn't get any louder. It seems to be coming from the back-left of the refrigerator.
How do I dertermine if it's the condenser fan or the evaporator fan? Is it possible that it could be the compressor and I just don't realize it? How do I test to determine which part to buy? Any suggestions?
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