Solution

The sound of the iPhone 11 earpiece becomes smaller because the mono audio and phone noise reduction are not turned on. The following explains how to turn it on

1

1. Open the settings.
2. Scroll down to find the auxiliary function.
3. Click the Audio and Visual option under Hearing.
4. Click the switch on the right to turn on mono

2 If it has not been fixed, try the following methods

1. First turn on the iPhone 11 and enter the main interface. Find "Settings" in the main interface, click to open, as shown in the figure below:
2. Then click the "Sound and Haptics" option in the "Settings" option of iPhone 11, and click to open.
3. Finally, slide the small dot in the middle of "Ringtones and Reminders" to increase the size of the iPhone