Wiered engine noises??

[Sam 400]

When I start a new flight, even if i've closed and re-opened the programme then the engine noise from the previous aircraft sounds. Lets say i've been flying a cessna skylane and load a new flight with a boeing 747 then it sounds like a cessna skylane!! Whats happening to it? It's just a bit annoing! please help.
Sam

[Sam 400]

I've had a play areound and if i restart my PC then it works fine. It only happens occasionally now, still i'd like some help to sort that now. Cheers,
Sam