Пропадает звук, появляется после перезагрузки
The sound disappears, appears after a reboot.
This is ENGLISH forum, for this reason yours text is translated with Google Translator. If you have trouble with ENGLISH, use Google translator in future 
About yours problem:
1. Did you tried Safe Mode - to check maybe 3rd party apps blocking sound and ect?
2. Did you tried Diagnostic app to check is problem with yours speakers?
3. Did you tried repair with Xperia Companion yours smartphone - often repair process (reinatslling software) helping to fix problems like this?
If nobody will not help i advise you to bring to authorized service in your location to check with professional diagnostic tools, maybe problem is with speakers detail
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