pmdg 747 engine sound problems

hi all,just got my pmdg 747 loaded into a flight and the most annoying and strangest thing is happening to the soundfirst of all in cockit view and virtual cockpit i cant hear the engines and i cant enjoy the flight.instead of hearing the engines spooling at full power in the cockpit all i can hear is a sound like air conditioning being on and its really loud then if i go outside the plane i can hear the engines as soon as i go back into the cockpit there no sound just the annoying air conditioning sound i have tried muting the sound.changine the sound options in fsx changed the pmdg sound options sound to normali have never had this problem before with this addon and am completley shocked as i cant seem to fix it.i need the proper sound in the cockpit as sitting the listening to nothing but air conditioning is very annoying.the addons i have installed are rex 2.0 and ftx australia sp3 i dont see these as being the culprits as the engine sound in the cockpit was fine last time i flewi have also tried the rolls royce pratt and whittney and the general electric variants and still no engine sounds in the cockpit whether there at full throttle half takeoff or landing even on engine start i cant hear them.all the sounds in my other games are fine and as all my musici have recently done a full reinstall of fsx and pmdg 747 and now i am having this problem.thanks hope i get this fixed and in the meantime i will play my other games as i cant enjoy my fsx without the pmdg sounds working properly.i have also ran a dxdiag to see if my sound drivers were not working correctly and all seems fine in there.im not sure if this is a DLL issue blocking the sound set or not.thank you hayden walker