I just got a 2020 i3 MacBook Air and have an adaptor to connect it to my monitor over HDMI port (which I plug my headphones into) but when I try to listen to anything the sound is way too loud. I've tried going to display and changing the volume but the slider does not work (it is fixed at the top).
The monitor is a Dell HDMI monitor. The sound is unusable like this. What can I do?