There is a simple and easy way to make sure the speaker of your pc will stop beeping everytime you issue a wrong command.
Try
sudo lsmod | grep pcspkr
If you can see
pcspkr
Turn it off
sudo rmmod pcspkr
Don’t forget to make the change permanent
sudo echo "blacklist pcspkr" > /etc/modprobe.d/blacklist-pcspkr
Job done