Sharing your system audio lets you stream your computer audio to meeting participants through Teams. You can use it to play a video or audio clip as part of a presentation. This feature is available for Windows users and not yet available for Apple users.
Include system audio
To share your system audio, select Share in your meeting controls and then Include system audio. When you share, all your system audio, including notifications, will be included in the meeting.
Note: Teams and your computer need to be set to the same speaker. Adjust your computer’s audio output in your system settings and your Teams audio output in your device settings in Teams.
Include system audio in a room with a Teams device
Teams devices allow you to share content using cables connected to the room console. Unfortunately, we do not yet support sharing system audio this way.
If you want to share system audio when you’re in a meeting room with a Teams device in it:
Join the meeting from your personal device by selecting Audio off when you join the meeting, which will automatically mute not only your microphone but also any audio playing from the teams meeting to prevent echo.
Select Share in your meeting controls and then Include system audio.
To avoid echo, remember to keep only one device’s mic and speaker on in a room.
Try to minimize the number of apps you run while you’re sharing your system audio. If your computer is running too many apps, your audio could suffer.
Reference: Share system audio in a teams