iphone11 often automatically adjusts the volume

iphone11 often automatically adjusts the volume because the volume is set to automatically adjust the function. The solution is as follows:

1. Click to open the Settings app, as shown below.

2. Find and select the option to turn on Face ID and Password, as shown below.

3. Then enter the mobile phone password to enter the function, as shown below.

4. Finally, turn off the annotation awareness function, as shown below.