Terrible Noise on Aircraft Selection

Hi Folks. Does anybody know please, why I get this dreadful loud jet engine noise when I select a flight in the Free Flight panel. Even a Cessna. It is not airport surrounding noise as I still get it on a farm strip, when I first enter the cockpit on aircraft selection, whatever airplane it may be. If I scroll through the various views using 'S' key tower, spot views etc, when I get back to the cockpit view, the horrendous noise is either cut by 80% or it has gone. If I then click on any of the tabs, i.e. World to get to Time and Season, when I return to the cockpit view the noise returns, and I have to scroll through the various views to get back to the cockpit view where again the noise is either eliminated or cut by 80%.

Does anybody know what on earth is causing it, and how I can remedy it.

Thanks Folks.

John