Comment 54 for bug 1254884

Ok, then I guess xfce4-volumed is accessing alsa directly, instead of doing the muting through pulseaudio.

Explanation for the inconsistency between muting and unmuting: xfce4-volumed sets the Master switch to muted. PulseAudio notices that something happened in the alsa mixer, and sees that one of the switches is muted, so PulseAudio concludes that the device is muted and sets the internal device state to mute. While setting the internal state, pulseaudio also mutes the rest of the switches marked as "switch = mute", including PCM. When xfce4-volumed unmutes the Master switch, PulseAudio again notices that something happened, but since the PCM switch is still muted, PulseAudio concludes that the device is still muted and does nothing.

xfce4-volumed should be changed to talk to pulseaudio instead of accessing the alsa mixer directly.