"Static" coming from passenger sight (RHS) tweeter at higher speeds

Good day all :)

I have a bit of a weird one - I have been noticing that when on the highway, the passenger side (RHS for us in CZ) tweeter makes almost like a static noise. I am pretty sure it is not related to the engine's RPM because if I rev the car at slower speeds I don't notice anything, and if on the highway I put it in neutral or hold the clutch and let go of the throttle for the RPMs to drop the noise stays there.

Any ideas what it could be? I am suspecting maybe an airleak somewhere - but have you had any such experience and is there something to look out for? P.S. I am not 100% it is the tweeter, it could be the door speaker, but since I am almost always on my own on the front (wife sits with the baby at the back), it is hard to identify the exact source.

Thanks