Compressor Sound from Engine on Start and Acceleration.
I am recently mentioned change in my engine sound, and I hope that someone here already had similar problem. So - recently my engine started sound louder, that it usually is - especially, when I accelerate. The sound is similar to compressor sound, and the faster I accelerate, the louder it gets. (Tho my radio sounds louder, even on max acceleration). I'd say it starts when RPMs gets over 3. It gets quieter once I am stop accelerating.
My main question - is it dangerous? What could that be? And how do I fix it? Thank you for your answers.