Chosen Solution

Hello Im from Italy and have a problem with my iphone 8, the audio calls is low but the music or something else is Ok I have already changed the upper audio speaker but the problem still exists Can you help me identifing the problem? is the ic audio chip? Thanks Roberto

there could be dirt in the speaker grill which is blocking out some of the sound

As Daniel said, ear speaker grill is clogged. Common problem with iPhone.