[Q] no notification sounds, speakers and audio clips work topic

When an alert, such as a text message, facebook message, or calendar alarm triggers on my Nexus 4 (5.0.1 lollipop, all stock no root), no sound is generated. The LED blinks and the phone vibrates (which is nice) but the audible alert is missing. The ringtone thankfully works, as well as my alarm clock and pandora, so I know that the speakers are operational. I checked every setting I can locate in reference to notifications, including volume settings, notification tones, app notification settings, and so on. Priority and Silent are NOT selected, volume is basically at max, and I have custom tones set up for mostly every app that will allow me to select one. No apps have notifications suppressed. The tones work when I select them in the menu, and the problem does not seem to care what specific tone is used.

The phone was factory reset Saturday (2 days ago) when I switched to it from my last device. Any insight as to what I should check next?