Loudspeaker no longer loud

For several months now my loudspeaker and earpiece volumes have been very low. I’ve checked all the settings, including noise cancellation, etc, and no difference. An Apple rep told me my battery could be the cause…so I changed that and after several days of using my phone there’s no improvement. Should I go ahead and just change the speaker and earpiece assemblies? Or is there something else I can check? Thank you.