If you are having problems hearing callers or meeting participants whether using internal speakers or external headphones, you can try the following to resolve the issue:.
Check that you are adjusting the volume for the correct device, e.g. USB headset rather than the internal speakers. Right-click on the speaker icon in the taskbar and press the upward arrow to select/identify the correct playback device.
Launch Teams and click on your profile picture.
Then click on Settings.
Select Devices.
Use the drop-down menu to set up the Audio device you want to use (speakers/headphones).
That will be your active device during Teams meetings and calls.
You can also check your settings while in a Teams meeting:
Click the three dots and go to Device settings. Make sure your speakers or headphones are set as the audio devices to be used with Teams.
Another thing you can check is your volume settings in the Volume Mixer.
Right-click on the speaker icon in the bottom right-hand corner of the task bar and select Volume Mixer
You will then see a window similar to below. Use the scroll bar at the bottom of this window until you see the Teams app.
Check that the sound isn't muted
for the Teams app and adjust the slider if necessary.
If the above still haven't resolved your issue, you can run the Troubleshooter:
Go to the Start menu (bottom left on task bar), select Settings → Update & Security → Troubleshoot (left pane).
Click on Playing Audio and run the troubleshooter.
If you still have no luck, please try an uninstall and reinstall of Teams, following this solution: https://freshservice.domino-printing.com/a/solutions/articles/50000071872