At irregular intervals, my MacBook Pro is emitting a chime. Not the startup chime. More of a brief "alert" type sound.
A few minutes will go by, no chime. Then chime, or several in a row. Then silence for a few minutes, etc.
I clicked notification center when it occurs to see what it's trying to alert me about. There are no notifications listed within the last hour.
I went through everything in notifications control panel and turned off audible alerts.
I turned on "do not disturb."
Power is 100%. Machine is plugged in. Light on power input is green.
Wifi is turned off. Ethernet connection is ok.
Retina MacBook Pro mid 2012.
OS X Sierra 10.12 (16A323).