whistling sound from engine bay when cold
 

So the car has been sitting for 2 weeks or so, and I drove it for the first time yesterday and noticed something odd that I have not heard before.

When it's cold, for the first 5 minutes or so, I notice a whistling sound coming from the engine bay that increases in frequency as the rpms go up, although I can't hear it after like 4k rpms. After about 5 minutes of driving the sound goes away, which to me dismisses a vacuum or exhaust leak. It does not make the noise at idle, and even when I'm stationary and do quick revs I can hear it, it does not need to be under load or at speed to be audible.

Any idea? I'm guessing possible belt or pulley, as it's consistent with rpm change and goes away once warmed up. Car has 11k miles.

I've recently noticed this as well this past week since it has been very cold. I don't remember if I was hearing this during the last winter.

Currently at 53k

Hear it when really cold as well. I am pretty sure you guessed right on the belts though. That rubber can get pretty firm in the cold.

I got the same thing going on, must be extremely cold though, like -20c