Call apple care first
Search the Apple website for troubleshooting help. If that doesn't help, I recommend making an appointment with Apple genius bar.
If you've performed all the self-help steps: - Making sure nothing is covering or obstructing the apeaker openings. (Screen protectors or cases covering them.) - Dust/debris plugging up the apeaker openings. (Try gently brushing away dirt/debris) - Checking all volume level settings. Then it may be appropriate to set up a service appointment at an area Apple Store. Reservations are strongly recommended.
Go apple store
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