Why is my phone playing the notification sound when the screen rotates?

[AC Question]

My phone started, all of a sudden, playing the notification sound whenever the screen rotates. I changed no settings or downloaded any apps. I do believe the phone updated, but I'm not positive about that. I can't find any settings that would cause this, even in developer settings. My phone is an LG G Flex 2 running 5.1.1.