Notification sounds for store apps are those sounds that are played in case of new notifications by any Store app. There is a setting in Windows 8 that allows you to turn these sounds on or off. In case you want to make changes to them, here is the tutorial you need to see:
1. Open up the Charms bar by moving your mouse to the top right of the screen. Now click the Lens icon to Search.
2. Type notifications in the search bar. Click Settings. On the left hand side, you would see a range of options. Click on Turn notification sounds on or off.
3. Turn the slider to either on or off under Play notification sounds to enable or disable the notification sounds.