A now software update is available, but during the first reboot makes some frightning beep sound? Don’t be afraid, we tell you the reason for this behaviour.
First, you will think of an update error: beep sounds normally indicate some serious problem before loading the operation system. In this case, however, it is a firmware update that comes included in in the macOS software update.
The Mac notices the firmware update, beeps, reboots and installs the new code. You can see that as the Mac show a thick progress bar (in contrast to the thinner normal one). After the installation of the new firmware, the Mac reboots again and continues with the software update process.
Interesting side fact: an iMac 27″ Mid 2011 now has a newer firmware version than listed on Apples site. Maybe the documents get updated a bit later.
