There is no sound when Apple 4 phones play songs outside. Just plug in the headphones. What happened? SMS only vibrates without sound. Why? Ask the great god for help!

This situation belongs to headset mode.

It should be caused by the failure of this microswitch, which means that the earphone has been pulled out, but the switch has not been turned off in time.

You can try plugging in headphones a few times quickly and see if you can make the logo disappear.

If not, it's time to change the earphone hole.

The headset mode will automatically switch. There will be a mark when the earphone is plugged in.

This is because there is a small microswitch in the headphone jack. When the headset is plugged in and the switch is touched, it will switch to headset mode.

If you unplug the headset and turn off the switch, the sign will be cancelled.