How to Clean iPhone Speakers
 

There are three main ways to clean your iPhone speakers. You could use a soft-bristle toothbrush to scrub the speaker. You could use canned air to blow debris out of the speaker’s nooks and crannies. Finally, you could use adhesive tape to remove the gunk trapped in or around the speaker. If you’re having trouble getting the speaker to play, clean the headphone port, too.

https://www.wikihow.com/Clean-iPhone-Speakers

How do you clean your phone?