To disable order notification sounds in NinjaTrader Desktop, you can do the following:
Open the Control Center in NinjaTrader Desktop
Select Tools then Options
Scroll down to Sounds in the General section
Click the x in each sound to disable it
Click OK and restart NinjaTrader Desktop
You can also disable order status notifications in NinjaTrader Web and NinjaTrader Mobile by doing the following:
Navigate to Application Settings in the NinjaTrader Web platform
Select the Preferences tab
Scroll down to Notifications
Toggle Order notifications off
Select Advanced Configuration to customize notification settings