Default Earpiece volume very low

Hey there, for no apparent reason my earpiece started emitting very low volume. I'm running the stock 4.1.2 ROM:

Android version: 4.1.2
Baseband version: APQ8064/MDM9x15M
Build number: JZO54K
Software Version: E97020j

I've been running bone stock since owning the phone brand new (it's the wife's).

Another user posted the same issue that was resolved via hardware replacement of the earpiece. I've just replaced the earpiece on my phone but still experience the extremely low volume. I've restored to stock to no avail.

Any ideas?