A truncated system notification sound will be heard if the start menu POWER=Shutdown or the Start Menu right click "shut down or sign out"=shutdown is used. Testing the default control panel sounds has the system notification be the closest to the brief musical sound I hear. There is not an actual 'shut down sound' displayed in the list.
A short cut icon with the shut down script 'C:\Windows\System32\shutdown.exe -s -t 00' does not produce this sound.
The event viewer report at shutdown time displays the Client OOBE ID 3 stopped. (Why this is listed as an error is a mystery since the security would be stopping if the machine is shut down???but that is the only event listed)

This little sound started after the Jan updates.
Previous to Jan and Feb updates I could not expect a complete shutdown if an external drive was plugged in.
After the recent updates the external drive can be left plugged in and the shut down does not restart.
That little sound is nothing compared to restart but I wondered if it needed to be investigated.