For ikke å høre P3D sin ATC når du er på vatsim går du til sound setting i menyen, sett voice slideren til 0. I samme menyen(hvis jeg husker riktig) velger du hvilke lyd du vill spille til hvilken lydenhet..
Forøvrig henviser jeg til dette som er sakset fra http://www.prepar3d.com/SDKv2/LearningCenter/getting_started/options/simulation/sound_settings.html
"Using a Headset
Using a headset for voice communications in Multiplayer air traffic control will add a great deal of realism. Your hands are free to fly the aircraft or to push buttons if you're the air traffic controller.
To use a headset in Multiplayer
Be sure the headset is plugged into the correct port on your computer.
Enable the voice communication host options.
During the session, press and hold CAPS LOCK to talk to other pilots or air traffic control. Release CAPS LOCK to stop transmitting.
IMPORTANT: There are a couple of things to know if you're going to use a headset. For the most realism, you only want voice communication coming through the headset.
If your headset is your only audio output, all sounds will come through the headset, including engine noise, wheels on pavement, and even e-mail notifications if you have your e-mail client running.
You must have two or more audio devices (sound cards) in your computer to enable voice-only audio through your headset.
To enable voice-only audio on a headset
(Two sound cards required)
On the Options menu, point to Settings and choose Sound.
Under Windows sound devices, select your headset in the Voice list.
To Enable or Disable Muting Sounds When Application Loses Focus
When the application loses focus, sound is muted by default. Disabling this setting requires editing the Prepar3D.cfg file.
Locate the Prepar3D.cfg file which can be found in the %APPDATA%\Lockheed Martin\Prepar3D v2 folder.
Right click file and click "Open", "Edit", or if prompted choose notepad or your other favorite text editor
In the [uSERINTERFACE] section, add MUTE_ON_LOST_FOCUS=0
To enable muting on lost focus, change it to MUTE_ON_LOST_FOCUS=1
Save the newly updated Prepar3D.cfg"