Xiaomi
Turn Screen Locking Sounds On or Off auf Xiaomi
The click you hear when the display turns on or off comes from a dedicated audio feedback option inside MIUI. Xiaomi built it as a confirmation sound, similar to keyboard clicks, so you notice when the screen state changes without looking at it.
The setting lives outside regular notification sounds. Adjusting media volume or Do Not Disturb does not touch it, because it is tied to system feedback, not to alerts or Focus mode.
To change it, open Settings ➔ Sound & vibration ➔ Additional settings ➔ Screen locking sounds. Switch the toggle off to mute the click, or turn it back on if you want the audio cue again.
If you actually want to quiet notification tones or reduce interruptions during calls and meetings, this toggle will not help. Check notification sound settings or Focus mode instead, since those control alerts, not the lock feedback click.
Turning off Screen locking sounds has no effect on vibration feedback or other haptic cues. Those are controlled separately, so you can keep vibration while removing only the audio click.