To disable the system beep during the shutdown -h +time, sysfinit has to be downloaded into your machine.
apt-get source sysvinit
vim sysvinit-2.88dsf/src/shutdown.c
then find a “void warn(int mins)” function and there change
wall(buf, 0); to /*wall(buf, 0);*/
then run ./configure make etc. or make a package. Also you can use this:
rmmod pcspeaker
Surely there is another way to off the beep which I do not know 😉