Dell inspiron 15 3521 no sound can be heard

Hello,

       I have a Dell Inspiron 15 3521. The problem is that there is no sound from the internal speakers nor from the microphone. When i do boot my laptop there is sound from both the sources but after few mins there is no sound at all. what do i need to do.

      I would greatly appreciate any help i get,

Thank you,

Maclaron