In an interim build of Windows 8 while it was under development, we were able to speed things up considerably by moving the shutdown sound from Explorer.exe (which is running while you’re still logged on) to Logonui.exe (which is the process that shows the 'Shutting down' circle.)
As part of speeding this up, we experiment a lot with what process is in control of the startup and shutdown sounds. We pay a lot of attention to how quickly the machine powers on, powers off, goes to sleep, resumes from sleep, etc.
'We removed these sound events for performance reasons. There is the official statement from Microsoft which explains the situation. Even if you assign sounds to the events for 'Exit Windows', 'Windows Logon' and 'Windows Logoff' or try to restore these events using the Registry, they will not play. In Windows 10, Microsoft focused on making Windows boot and shut down faster. Developers of the OS had completely removed the sounds which play at logon, log off and shutdown. Play the Shutdown Sound in Windows 10 Why Windows 10 doesn't play the shutdown sound
