I found an easy way to turn on/off all sound.
Just replace disable with enable to turn it back on.
The tricky part is in getting a unique string that just returns the device you want off.
Use devcon find *<string values> to make sure you have the right device.
During testing, I ended up turning off my mouse. :-)
:: off_noise.bat Turn off computer speaker and sound board
::
devcon disable *ACPI\PNP0800
devcon disable *3059
Is mute not quiet enough for you?
Mute does not turn off computer speaker.