Front Earpiece Speaker quiet, no damage, CAN'T HEAR why?

Overnight the speaker on the top used when making phone calls volume has become so low that i can barely hear the other person or my voicemails.

The speaker phone works just fine, and there has not been any drops or water damage and it was working fine just last night.

Why should this happen? I can only assume water damage but there was none.

do i need to replace it? is it replaceable or is it part of the whole front screen assembly?

Please help, now i need to use my headphones or speaker phone for every call.