iphone Apple phone lock screen no sound what to do

1. First on the IPhone home screen to find the "settings" icon, click Open, as shown in the picture
3. 2
   Find the "sound" option in the Settings list and click Enter as shown in the picture
4. 3
   Locate the lock sound option in the Sound Settings list, as shown in the figure
5. 4
   Then turn off the lock sound and then open it. Then try pressing the iphone's Power Lock button to confirm that there is a lock sound, as shown in the picture
6. 5
   If you reset the button in the settings and then turn it back on, there is no sound. Next, hold down the "power lock" button on the top of the Apple phone until the slide shutdown screen appears, and then slide off the machine as shown
7. 6
   Wait until the shutdown is successful, and then press the top of the Apple phone "power lock" reboot, and finally try to lock the screen to confirm whether there is sound.