whine near 3000 rpm

[tff]

I've searched this forum and the web regarding the below, but haven't convinced myself that what I heard was normal or not. Having said that... here's my situation...

I test drove a 986 Boxster S today. The car was great, except I was bothered by a somewhat mechanical-sounding whine around 2800 to 3000 rpm (all gears, and in neutral) coming from the engine area (from inside the car, top up). I noticed it right away and frankly it was somewhat annoying (but only near that rpm).

I'd chalk this up to being 'normal', but I drove another similar Boxster S (twice) a couple weeks back and I was only impressed by the engine noises... I don't recall hearing anything like this on that car.

(For those that may have experiences with a 944, the sound is similar to that made by a balance belt shaft that is not correctly tensioned).

Any thoughts on whether what I experienced is normal? What could be causing it if not normal? I'm thinking that maybe variation in engine tolerances is contributing to differences in the two cars?...

[Geof3]

Any white smoke or otherwise? The AOS can make some noise if it is on its way out. Do you know how to access the engine compartment? I’d open it up, run it and see if you can find the source. If it is the AOS making the noise it should be pretty obvious.

[Anker]

A bad bearing on anything pulled by the serpentine belt will often make that kind of whine.

[tff]

Thanks for the comments thus far. The below video highlights the same kind of noise I heard (I know that this is a 987 vintage & a cayman, but sounded similar).

https://www.youtube.com/watch?v=3JWo9HpTgws

So the car did have a puff of whitish smoke from the tailpipe on start-up. I'd say it lasted for about 5 seconds max but was 'obvious'. Thoughts on whether this is normal or part of the air-oil separator issue? (Also, my understanding of the noise caused by the AOS is that it's when the engine is cold only???)