FSX sound enabled when in background.

Flight1 SoundStream Released
Flight1 Software announces the release of Flight1 SoundStream.  This ingenious tool keeps the Flight Simulator sound enabled even when FSX is running in the background. It lets you use add-on programs developed for Flight Simulator (such as moving maps) without interrupting the in-flight sound experience. Or you can read and answer an email or surf the web during a long flight – all this without your ears leaving the cockpit.

No more missed ATC calls and any warning sounds, and of course you will hear that the engines are still running!  Flight1 SoundStream runs as a module inside Flight Simulator and can be configured using the Add-Ons menu during the flight. You can enable and disable SoundStream at any time. And optionally, you can set a reduced sound volume to be used when FS is running in the background.  Get Flight1 SoundStream now, and enjoy a more complete sound experience with FSX and Prepar3D!  For more information on this product and a video demonstration, visit this site.

Source: http://www.flight1.com/products.asp?product=soundstream