Go to [Settings]-[Sound] (For Android O: [settings]-[sound&vibration]), drag the Ringer, Alarm and Media Volume sliders to the right side to increase the volume;
Clean the speaker hole with a soft brush to check;
Check if it just related to a specific APP, if yes, Check if the APP version is the latest version, if not, please update APP to the latest version to check;
If the problem remains, keep your phone updated to the latest software version and reboot your phone to check if it is OK.
Yes
No
