If you use the volume control in the tray, checking and unchecking the mute box should work.
Then use the mute button to see what else is muted and NOT unmuted.
If you do not have a volume control in the tray, right click on the tray and select Panel Settings > Panel Applets > +Add > Volume Control.
Otherwise...
If you would like a keyboard shortcut,
I create a shell script with the needed commands,
then assign the shortcut to the script in openbox.
Often the mute button will turn off more than the Master.
You will need a script to unmute;
for example PCM, Headphone, Speaker, 'Master Mono' ...
First open terminal and type: alsamixer
The alsamixer will graphically show the audio card and chip used and which controls are available.
Which card and chip does your computer use?
To find the names of the controls, in terminal type: amixer
On my Dell d420 the mute button works, for your Dell you need more controls.
The following is a list for controlling mute for several audio chips.
# .......1.........2.........3.........4.........5.........6....
# card:HDA Intel chip:SigmaTel STAC9200 # Dell d420
amixer -q set Master toggle
# .......1.........2.........3.........4.........5.........6....
# card:Intel ICH8 chip:Realtek ALC268 # Toshiba dv3000
amixer -q set Master toggle
# .......1.........2.........3.........4.........5.........6....
# card:PulseAudio chip:PulseAudio # eeepc 701 debian 8.6
amixer -q set Master toggle
amixer -q set Capture 0
# .......1.........2.........3.........4.........5.........6....
# card:HDA Intel chip:Realtek ALC662 rev1 # eeepc 701 ubuntu
amixer get Master | grep -o off \
&& (
amixer -q set Master unmute
amixer -q set Headphone unmute
amixer -q set Headphone 100%
amixer -q set Speaker unmute
amixer -q set Speaker 100%
amixer -q set PCM 100%
) || (
amixer -q set Master mute
amixer -q set Beep mute
amixer -q set Beep 0
amixer -q set 'Auto-Mute Mode' Disabled
amixer -q set 'Loopback Mixing' Disabled
)
amixer -q set Capture 0
# .......1.........2.........3.........4.........5.........6....
# card:Intel ICH6 chip:Analog Devices AD1981B # HP nc6220
amixer get Master | grep -o off \
&& (
amixer -q set Master unmute
amixer -q set 'Master Mono' unmute
amixer -q set 'Master Mono' 100%
amixer -q set 'Headphone Jack Sense' unmute
amixer -q set PCM unmute
) || (
amixer -q set Master mute
)
# .......1.........2.........3.........4.........5.........6....
# card:Intel ICH5 chip:Realtek ALC650F # Shuttle
amixer get Master | grep -o off \
&& (
amixer -q set Master unmute
amixer -q set 'Master Mono' unmute
amixer -q set 'Master Mono' 100%
amixer -q set PCM unmute
amixer -q set PCM 100%
amixer -q set Surround unmute
amixer -q set Surround 100%
amixer -q set Center unmute
amixer -q set Center 100%
amixer -q set LFE unmute
amixer -q set LFE 100%
amixer -q set Beep 1
) || (
amixer -q set Master mute
amixer -q set Beep mute
amixer -q set Beep 0
)
# .......1.........2.........3.........4.........5.........6....
# card:HDA Intel MID chip:Realtek ALC259 # Toshiba Satellite L675-129
amixer get Master | grep -o off \
&& (
amixer -q set Master unmute
amixer -q set Headphone unmute
amixer -q set Headphone 100%
amixer -q set Speaker unmute
amixer -q set Speaker 100%
amixer -q set PCM 100%
amixer -q set 'Auto-Mute Mode' Disabled
amixer -q set 'Loopback Mixing' Disabled
) || (
amixer -q set Master mute
amixer -q set Beep mute
amixer -q set Capture 0
)
# .......1.........2.........3.........4.........5.........6....