You did not have the defrost on still did you? Defrost still will cycle the a/c compressor. Turn off the climate control all together. Also you could take the drive belt off and start the vehicle. If the noise is gone its not anything to do with the timing belt and leaves you with just the serp belt driven components.If I turn off the A/c inside the car you can still hear the sound,but doesnt the ac compressor run all the time regardless if its still on in the car or not?