There are ways to determine what it is, the most important question is when the noise comes back do you hear it in the engine compartment as well? Does the pulley for the AC continue spinning or click off?

It could be the air vent is clogged as well and making a "sucking" sound through the dirt. It is really hard to guess. But clogged filter = less air movement = less cold air. But that is only if the rest of the system functions properly.