On this sound output page, you can:
- view all sound output devices (headphones, speakers, speakers, etc.) recognized by your Mac,
- select the one that will be used by default by clicking on it so that it is selected in blue,
- adjust the volume of the sound using the lowest bar,
- mute your Mac by checking the "Silence" box.
Note: if you're using a side app, don't expect an immediate change. It is often necessary to refresh or relaunch the application for this change to take effect.