I agree with Alan that it is a possible combination of psycho-acoustics and actual changes occuring in the body which could possibly alter your senses.

Cold is a threat to the human body so naturally there is some natural survival insticts/changes happening and it will alter your perceptions. Under "normal cold" within the threshold I would think there would be an initial attempt by the body to send warm blood to the brain, ears, feet, hands etc. When changes are occuring in the brain, anything is possible. It is possible under your conditions it could heighten the senses. Under extreme conditions over a period of time that warm blood will get diverted to save the brain and other vital organs and the "less important" areas such as the feet, hands and ears would be sacrificed. No bloodflow or reduced bloodflow in cold equates to frostbite and lack of sensation. I guess this could be equated to the sensation of your arm "falling asleep". Sensation/perception and blood flow are definitely intertwined \:D ( I won't go there) :D.
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