A PC Speaker is helpful as it could be used as a tool for diagnosing system hardware failures (different systems produce different beep sequences depending on the machine BIOS type).
Using the instructions for the respective BIOS vendor and version one could determine the type of problem experienced by a machine based on the sequence and frequency of sounds produced by the SPEAKER.
Lets say a hardware component on a server is down with no need for a monitor or screen to be attached you can say precisely if it is the hard drive, memory or fan malfunctioning…
Generally speaking historically embedded PC Speaker was inseparatable part of the Personal Computers, preceding the soundblasters, now this is changing but for compitability sake many comp equipment vendors still produce machines with pc-speaker in.
Some newer machines (mostly laptops) are factory produced with no PC-SPEAKER component anymore.
For those who don't know what is PC SPEAKER, it is a hardware device capable of emitting very simple short beep sounds at certain system occasions.
Talking about PC-Speaker, it reminds me of the old computer days, where we used pc-speakers to play music in DOS quite frequently.
It was wide practice across my friends and myself to use the pc-speaker to play Axel Folly and other mod files because we couldn't afford to pay 150$ for a sound cards. Playing a song over pc-speaker is quite a nice thing and it will be a nice thing if someone writes a program to be able to play songs on Linux via the pc-speaker for the sake of experiment.
As of time of writting, I don't know of any application capable of playing music files via the pc-speaker if one knows of something like this please, drop me a comment..
As long as it is used for hardware failure diagnosis the speaker is useful, however there are too many occasions where its just creating useless annoying sounds.
For instance whether one uses a GUI terminal or console typing commands and hits multiple times backspace to delete a mistyped command. The result is just irritating beeps, which could be quite disturbing for other people in the room (for example if you use Linux as Desktop in heterogeneous OS office).
When this "unplanned" glitchering beeps are experienced 100+ times a day you really want to break the computer, as well as your collegues are starting to get mad (if not using their headphones) 
Hence you need sometimes to turn off the pc-speaker to save some nerves.
Here is how this is done on major Linux distros.
On Debian and most other distros, the PC SPEAKER is controlled by a kernel module, so to disable communication with the speaker you have to remove the kernel module.
On Debian and Fedora disabling pcspeaker is done with:
# modprobe -r pcspkr
Then to permanently disable load of the pcspkr module on system boot:
debian:~# echo 'blacklist pcspkr' >> /etc/modprobe.d/blacklist.conf
On Ubuntu to disable load on boot /etc/modprobe.d/blacklist, file should be used:
ubuntu:~# echo 'blacklist pcspkr' >> /etc/modprobe.d/blacklistWell that's all folks …
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