so not to be obvious but you have one of two problems either hardware or software. there is a way to check but you need to do a few things. first you should try creating a new user account and see if the volume problem still exists. you create a new user through system prefs/accounts. if that doesn’t work you should try a pram reset by holding down the cmd, option, r, p, key at boot. IF you have never done this before you want to hear the startup chimes at least 3 times then let the computer restart. if that still doesn’t work you should try an archive and install of the os from the discs if you still have them, and if none of that work you most likely have a hardware issue and either the logic board needs to be replaced or the speakers are bad. but either way its going to cost money if there is a hardware issue and you might consider a new computer, im just being honest.
