How to pinpoint a noisy bearing or pulley

Question

My '98 Protege makes a high pitched whine for the first couple hundred yards when both the engine and outside temperature are cold (below freezing). It doesn't sound like a squealing belt. The sounds is an annoyingly high pitched metallic whine that increases in frequency (and volume) as the engine revs. I think it's one of pulleys (or bearings) on one of the accessories, water pump, or the A/C compressor, but I can't figure out which one when looking under the hood. I suppose it could also be one of the belt tensioners or idler pulleys. So, the question is this: how can I figure out which one is the culprit?

Answer 1

Rubber tubing is a cheap alternative to a stethoscope. You can buy a couple feet of it for a couple dollars at any hardware store, just be careful where you point it.

Thank Click & Clack for that, it worked for me.

Answer 2

Use an auto repair stethoscope or even a long socket extension as a substitute to listen to each pulley when you start the car.

If it's truly a bearing issue, you'll hear it right away when you find the affected part.