Xiaomi
Turn On/Off Mono Audio auf Xiaomi
Mono audio is an accessibility feature built into MIUI that merges stereo channels into a single audio signal. When it's active, both speakers, earbuds or a connected headset output the exact same content instead of separate left and right tracks. Xiaomi added this option for people with hearing loss in one ear, since it prevents audio details from being lost on the weaker side.
The setting affects every audio source on the phone: music, videos, calls, notifications and games all switch to mono playback once it's turned on. If you rely on spatial audio, game sound cues or stereo separation in music, leaving this option enabled by accident removes that separation completely.
To check or change the state, open Settings ➔ Additional settings ➔ Accessibility ➔ Hearing and toggle Mono audio on or off.
If only one earbud or speaker sounds quiet rather than identical on both sides, the cause is usually a hardware or Bluetooth balance issue, not this setting. In that case check the audio balance slider next to Hearing or clean the speaker grille instead of touching Mono audio.