I have a Nexus 4 running Android 4.4.2 (not rooted, but with developer options enabled), and it keeps developing a stuck looping sound (I guess part of a notification sound, looping approximately every second). It survives shutdown / restart, and I've been through killing processes and services, and apparently at random at some point after killing everything, it sometimes seems to stop (sometimes it keeps going no matter how many you kill)...
...but it keeps coming back. I'm at the 4th or 5th time in 24 hours where I think it is fixed, only to find it bleeping away later. Obviously this makes it hard to leave the volume on!
So: any ideas on identifying the offender? Maybe some tool that can display the sound buffers by originating process? Or just flush them...
Note: it also survives a reboot into safe mode, continuing to play in a loop while in safe mode.