Turn Off Interface Sound When Trying to Empty an (Already) Empty Trash

Another test you can try is to boot into Safe Mode (How to use safe mode on your Mac - Apple Support) by booting with the Shift key held down and check there to see if the problem persists.  Reboot normally and test again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing some system cache cleaning, volume verifying and directory repairing. 

Hello mike881,

I understand that your computer continues to play a sound when an (already) empty trash can is being emptied. You've turned off the user interface sound effects and yet the sound still plays. I can see how this could be an issue. Can you tell me a little bit more about what troubleshooting steps you may have taken? In the meantime here are few steps I would suggest:

1. Select and then deselect the "play user interface sound effects" box.
2. Empty trash again to verify if issue persists.
3. Restart the computer and try again