When I have the AC on there is an intermittent whistling sound from the passenger sound. It is not from a partially opened/closed vent otherwise it would not be intermittent and I here the sound regardless of what position the passenger vents are in. Any idea what could cause this ? The car is at the dealer so I would like to here ideas as soon as possible. The car is 4.5 months old.

 

maybe the filter got clogged up already? I dont know what else could cause the sound. something restricting the air....someone who knows more will come save the day im sure.