audio is not working on dell inspiron 14z

hi!!!
i m using dell inspiron 14z 5423 with windows 8.having a problem with my audio when i start my laptop for some time (2 to 3 min) it play sound than it dont play sounds.sounds disappears. even it dont respond to mute when it click on mute button of speaker showen on right lower corner..
plxx help coz itx very irritating..