I'm running MIUI 3.9.20, the English Version, on a Xiaomi M2A. Certain sounds are just way too loud when you use headphones. It seems that MIUI/Android has several categories of sounds/volumes: media/game sounds, interface sounds, voice volume, ringtone/notification/alarm sounds. You can adjust the volume for these things separately. The media sounds are fine on headphones, the voice volume is fine, the interface sounds (e.g. button presses) are fine too. But the ringtone/notification/alarm sounds are simply earshattering. It seems that the category of sounds that use both the speaker and headphones simultaneously are just way overpowered.