Q: Sound stopped working when iPhone 6 is on lock screen iOS 9.2

Hello Equang,

Thank you for using Apple Support Communities. 

If you are having issues with the sound on your iPhone, the following article is a good place to start troubleshooting. 

If you hear no sound or distorted sound from your iPhone, iPad, or iPod touch speaker

If you are unable to resolve the issue with this article, please post back with more information about what is going on. What sounds are not working, ring tones, alarms, etc? Music? 

Happy New Years.