If you're running Windows 10, check this out:
How to Set Per-App Sound Outputs in Windows 10
Windows 10 now lets you choose which sound output and input devices individual apps use.www.howtogeek.com
In your Sound Control Panel, go to Advanced sound options and App volume and device preferences. There you can select which device is used for each application. Set your game to use your headphones and your browser (for YouTube) to speakers.
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