How to disable all notification sounds in Android 6? I want the simplest way to say that I should never hear audible notifications from apps. 

I don't want to have to configure apps individually, and once I set all app notifications to mute, newly added apps should still be mute.

I am happy to install a new app to do this, if needed.
Go to Settings>Sound &amp; Notification>Volumes and tap on 'Notification sound' icon to mute it or drag handle to the left.
Or press Volume + or - than expand volume panel and drag handle to the left or tap icon (for notification sound)