Audio - Almost inaudibly soft in Video meeting

Hi, 

When I start a Video meeting in MicroSoft Teams, the sound is inaudibly soft. The strange thing is that the audio volume is normal in all other applications. Even the volume of the waiting tone before the meeting is good. If I plug in a headphone, the sound is also good.

My settings:

Windows Volume Mixer:

All maximized

Audio settings in MicroSoft Teams are good (as far as I can see):

What am I doing wrong?

Thanks in advance, 

Louis