Hi, I was just listening to my fan and wondering something: **from my chair, when the fan is on, I can hear a very clear "Pshhh". **but when I put my ear close to the air vent, I can hear a little "Rrrr - Rrrr - Rrrr" deep inside the "Pshhh", like a cyclic little mechanical noise. I was just wondering if this "Rrrr - Rrrr - Rrrr" is normal. I've never loved the mechanical noises. It's never a good sign. Is that serious, or is it absolutely normal doctor ? Thanks for reading !