If this function is enabled on the Xiaomi smartphone, the channels are connected during audio playback, which means that the left and right speakers play the same audio content.

Android 10 (MIUI 12.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Additional settings
Step 3:  Tap on  Accessibility
Step 4:  Tap on  Hearing
Step 5:  Enable or disable  Mono audio
  1. Open the Settings
  2. Tap on Additional settings
  3. Tap on Accessibility
  4. Tap on Hearing
  5. Enable or disable Mono audio

Xiaomi Instructions