All right then, by popular demand I will be the designated volunteer.
I probably take out the instrument cluster this weekend (the temperature display illumination is burned out, need to solder in a new bulb) and drive the car to see where exactly the sound is coming from. If I get around doing it I will post the findings. However it is definitely not coming from the speedo cable. I think jsmith is on the right track because it only started producing the noise when the outside temperature dropped (I park underground, and it happens once I am on the surface).