Shutdown beep on Xfce, but not on MATE or Openbox

[pccobbler]

I have multiple Sparky systems: Xfce, MATE, and Openbox. Xfce beeps on shutdown, which is annoying when I'm wearing headphones. I surfed around for a solution, but they're all over the map, with Ubuntu solutions not being relevant at all, not surprising given the relationship between Debian and Ubuntu.

Why is Xfce different? Can someone recommend a solution?

[paxmark1]

"Multiple Sparky Systems"   Is this multiple computers or multiple DE's on 1 computer?

  If you have multiple DE's on 1 computer the dot files ( .blah-config  _) in your ~ file  (~ == /home/yournameforhome) Some DE's will use the same name for certain items and that can cause conflicts.    If you have multiple computers, well, I do not use XFCE at present and others will have to help.   

As always, pet peeve of mine - not stating Stable versus Rolling  is something that should be done for most requests for help.   Also stating where you have searched prior to this forum if you have is helpful. 

[pccobbler]

Mea culpa.

The MATE is on an external SSD connected via USB. The Openbox and Xfce are on different USB flash drives (NOT LiveUSB, installed). Only one of them is connected at a time to my laptop (Intel 3rd Generation Core processor and 8 GB of memory), as I dislike multiple-boot configurations. I always remove the internal SATA Windows SSD when creating a new Linux system

The MATE is rolling, while the Openbox and Xfce are stable. I'd prefer all to be stable, but MATE is not offered that way.

I expected Openbox and Xfce to be similar in nature, as both are stable, but the former does not have the auto-update while the latter does. The Openbox does not beep on shutdown.