"party whistle" at 2.5k revs+

[F0zzie]

Hey all, new to ownership, loving it so far, been lurking and found it all very helpful.
New sound I couldn't find described anywhere. I have 2008 2.0l Z4. When it's warm I get what can only be described as a party whistle. Anyone have any clue?

https://youtu.be/9NoPzfbP8_I

Ta

 

[Chris_D]

Sounds like normal intake to me.
checked air filter?

 

[Street]

I don’t know but it made me smile. Perhaps it’s just a happy car

I’m guessing there’s a vacuum or air leak somewhere that when warm is expanding/softening just enough to let air through an resonate. Can you get someone to help pin down where in the engine bay it is?