Ford Focus - wooshing noise - richbev

my 1.8 diesel focus 56 plate just started making like a wooshing noise when i rev the car. here,s how it goes.

it sounds like its coming from the air vents inside the car when driving. this only happens when we rev the car hard and the turbo is working. i thought maybe a ppipe had come off on the induction side of things but doesnt seem to have. any idea,s folks please.