What happened to the sudden loud voice of Apple's mobile phone?

1, confirm whether the volume key is touched by mistake;

2. Whether the Bluetooth headset or other devices that can adjust the volume of the mobile phone are connected;

3. Restart the phone;

4. Enter Settings-System Management/More Settings-Backup and Reset/Restore Factory Settings-Restore all settings. This operation will cause the logged-in third-party software account to log in again, but it will not clear the photos, videos and other files stored in the mobile phone. Before restoring all settings, please make sure that the use of some third-party software will not be affected. In order to avoid data loss caused by abnormal operation, it is recommended that you back up the important data of your mobile phone first.