Silent notifications not silent

[Android Central Question]

All of a sudden a few days ago, all of the notifications I set to be silent are now making noises. They are explicitly set to silent in apps like YouTube, GooglePlay, MS Outlook, etc. But all of those apps are now playing sounds even when set to silent. This just started -- it's like the "silent" setting just stopped working. I have a Galaxy Note 8, with the latest Android build that came in a few weeks ago.

Help...