Set default sound output card dynamically using PulseAudio.

pactl list short sources

returns:

1	alsa_output.pci-0000_0b_00.4.analog-stereo.monitor	module-alsa-card.c	s16le 2ch 48000Hz	IDLE
4	alsa_output.pci-0000_09_00.1.hdmi-stereo-extra1.monitor	module-alsa-card.c	s16le 2ch 44100Hz	SUSPENDED

pactl list short sinks

returns:

1	alsa_output.pci-0000_0b_00.4.analog-stereo	module-alsa-card.c	s16le 2ch 48000Hz	RUNNING
3	alsa_output.pci-0000_09_00.1.hdmi-stereo-extra1	module-alsa-card.c	s16le 2ch 44100Hz	SUSPENDED

pactl set-default-source alsa_output.pci-0000_0b_00.4.analog-stereo
pactl set-default-sink alsa_output.pci-0000_0b_00.4.analog-stereo

!/bin/bash
 
declare -i sinks_count=`pacmd list-sinks | grep -c index:[[:space:]][[:digit:]]`
declare -i active_sink_index=`pacmd list-sinks | sed -n -e 's/\*[[:space:]]index:[[:space:]]\([[:digit:]]\)/\1/p'`
declare -i major_sink_index=$sinks_count-1
declare -i next_sink_index=0
 
if [ $active_sink_index -ne $major_sink_index ] ; then
    next_sink_index=active_sink_index+1
fi
 
#change the default sink
pacmd "set-default-sink ${next_sink_index}"
 
#move all inputs to the new sink
for app in $(pacmd list-sink-inputs | sed -n -e 's/index:[[:space:]]\([[:digit:]]\)/\1/p');
do
    pacmd "move-sink-input $app $next_sink_index"
done
 
#display notification
declare -i ndx=0
pacmd list-sinks | sed -n -e 's/device.description[[:space:]]=[[:space:]]"\(.*\)"/\1/p' | while read line;
do
    if [ $next_sink_index -eq $ndx ] ; then
        notify-send -i notification-audio-volume-high "Sound output switched to" "$line"
        exit

NOTE:

Before running the script:

• Set Permissions:

  sudo chmod 755 /usr/local/bin/audio-device-switch.sh

To allocate to a shortcut key:

• Navigate to System → Preferences → Keyboard Shortcuts.
• Click Add.
  • Name: Switch between audio devices.
  • Command: audio-device-switch.sh.
  • Press Apply.
  • Select the newly added shortcut row and click on the shortcut column.
  • Choose a shortcut combination – e.g.WIN + F12.

man pactl