The volume mute button on my laptop has a light that normally illuminates when muted:
Enable / disable speakers
I’ve learned that the light’s behavior can be controlled:
led='/sys/class/sound/ctl-led/speaker/mode' sudo tee $led <<< 'off' # never on sudo tee $led <<< 'on' # always on sudo tee $led <<< 'follow-mute' # on when muted sudo tee $led <<< 'follow-route' # on when NOT muted
The default is
follow-mute, but I prefer the inverted behavior
Confusingly, something seems to be watching the light and automatically muting the speaker when the light is illuminated. To demonstrate:
play -n synth brownnoise & # The speakers start making noise. sudo tee $led <<< 'on' # The speakers go silent. sudo tee $led <<< 'off' # The speakers resume making noise. kill %1
This is backwards; the light should not affect the speaker. It has the insidious effect that
follow-route just causes the system to mute itself in a feedback loop.
Why is this happening? I’m not sure what to investigate next.