No matter what device you have, sometimes your audio has problems. You can be experiencing very quiet sound from your ear piece, or no sound at all. These problems can be caused by many things, such as dropping the device, water damage, high heat, cold, etc., and each thing can cause failures for multiple reasons.
So, while often, this can be repaired by replacing a speaker, it is often the audio chip on the board that is causing problems, something preventing power to the audio chip, or something preventing the signal getting from the audio chip to the speakers.
Many iPhones have a flaw that Apple refuses to address, where pads lift off the board under the audio chip. We can repair this too.