What is the best way to turn off the Ubuntu beep permanently?

disable the warning beep you can do so by editing your /etc/rc.local file. Open the file in your editor of choice and go all the way to the bottom of the file. At the bottom there should be a line which reads exit 0. Add a new line directly above this one and put this on that line:

modprobe -r pcspkr. 

Save the file and this will turn off the system beep. If you want to turn the system beep back on, just edit this file again and remove the line that was added.

(OR)

You can disable this by editing a file and entering two simple lines.

gedit /etc/modprobe.d/blacklist

And then add:

silly speaker beep

blacklist pcspkr

Save your file and the speaker beep will be gone when you reboot.

If you don’t want to wait until a reboot, simply type:

sudo rmmod pcspkr

(OR)

You can disable system bell if in the Terminal you go to Edit->Current Profile->General and uncheck the Terminal Bell Or in the Configuration editor go to apps->Gnome-Terminal->Profiles->default check silent Bell.

(OR)

Edit the .inputrc file in your home directory (create it if needed) and add the line

set bell-style visible

You can also add (or uncomment) this line in the general /etc/inputrc file to set the bell-style for all users (overriden in ~/.inputrc).

Ubuntu 16, search the applications for Sound, click on "sound effects" tab, Set the alert volume under that tab to "Off"

Disconnect the PC speaker inside the Chassis.

That is the simple answer.