a Quick search led me to this page, where one answer states:
I had this issue on my ThinkPad T450s (Fn + F4 is toggle mic) on Ubuntu 18.04 and adding this line to my i3 config solved it:
bindsym XF86AudioMicMute exec --no-startup-id pactl set-source-mute 1 toggle
So perhaps something similar?
Edit:
I believe I’ve found something that can work, Look at: https://faq.i3wm.org/question/3815/execute-command-when-mod-is-pressed.1.html:
In my i3 config I put:
bindcode 133 exec my_command
Where ‘133’ is the keycode of my Mod key, then I can run my_command each time it’s pressed. So I can update my i3blocks bar by putting:
bindcode 133 exec pkill -SIGRTMIN+1 i3blocks
in the config, then all the blocks with a signal of 1 will be updated.
I believe this could be modified to suit your needs…
Edit 2:
Look at
https://www.reddit.com/r/i3wm/comments/2wbv8x/question_how_to_manage_audio_with_i3/