This was done with pulseaudio 8.0
So, here it is:
echo $(( ($(pacmd list-sinks | sed -n -e "/$(pacmd stat | grep "Default sink name" | cut -d ' ' -f4)/,\$p" | grep -m1 volume | cut -d '/' -f2,4 | tr -d '% ' | tr '/' '+')) / 2 ))Wow.. that's a mouthful. Let's break it down...
