Chosen Solution

My iPhone 11 Pro earpiece is rattling and has thin sound. How could I fix it? Should I remove the sensor array and and clean the speaker with alcohol?

Definitely try cleaning everything out with some alcohol, and make sure that you’ve removed all of the adhesive that may be underneath any components and use some fresh adhesive. If the quality of sound is still bad, then you may need to replace the earpiece speaker, which unfortunately comes with the FaceID, meaning replacing it would render FaceID inoperable.