FSX sound increasing (Please help!)

Hello everybody!

I have bought new computer last month and install FSX on it. The FSX is working normall, but when I parked the airplane and shout down the enginess, the sound of electricity appears (the electricity probably running the flight instruments - and that sound doesn't bother me), but in few moments that sound rapidly increase, and it is much louder than usual.

Can anyone help me?

I would be very happy any help!

Kind regards,
Tijan Derganc