To resolve the sound problem kindly follow below given steps:-
1. Disconnect all accessories and remove any third-party case form your phone and check device volume settings if its full or not.
2. Reset the device:- Kindly create data backup of your device via SMART switch mobile application or http://www.samsung.com/in/support/smartswitch pc suite. Tap on Settings>Tap on General Management>Tap on Reset.
If the issue still persist kindly visit your nearby service center for the physical inspection of your device. You can search for the nearby service center from given link:- https://www.samsung.com/in/support/service-center/
