You haven’t described your problem properly but if it is only an audio issue it would point to the audio IC. It is a signature fault with this model. If it also has any of the following symptoms it would confirm it.
These are the symptoms of audio IC failure on the 7 series.
· Callers can't hear you
· You can’t hear callers
· Voice memos are greyed out
· Sound doesn't record on videos
· Siri can't hear you
· You hear static on calls
· Speakerphone doesn't work
· Phone takes a very long time to boot
The audio IC repair requires microsoldering as jumper wires need to be installed.