Why is my air vent whistling?

Question

making a noise

Answer 1

do to too much air flow remove the vent cover and cut a piece of cardboard to fit the vent, then cut a small round hole in it to reduce air flow enlarge hole until you get the flow you want.  

Answer 2

no comment

Answer 3

You probably have something caught in there, i worked on a supermarket installing a kitchen hood and when they started up the exhaust fan it had a whistling noise, took ages to find out where it was coming from but all it was was a rivet head that was stuck in the grille.

Answer 4

Usually, whistling is cause by air blockage in an air vent. So If you have the air vent  closed, then it could be that it didn't close all the way, and that will cause the whistling, as the air is forced through the small gaps.

Hope it helps!