Muted all notification sounds - notifications still make sounds? -_-

[Android Central Question]

My notification sound is set to None and yet the phone still makes a sound when I receive a notification - happened with a Facebook notification most recently. I've also turned off in-app sounds from the Facebook settings, so what else is there left to do? I don't want to stop push notifications at all, I just don't want beeps coming out of my phone.. Thank you in advance!