Yeah I know what you are referring to it is similar to when the system is getting ready to print, when the printheads go through the maintenance kit (behind the screen), but it is not that.
I posted on another forum and they suggested that there is definitely an air leakage, and the air pumps are trying to compensate for it, makes a lot of sense imo, what's frustrating is that the tech guys that changed the pumps said that it was normal even after I told him the machine didn't do that noise before.