My laptop cannot play sound

after my laptop was switched on it works properly for sometime then sound stops playing after a half an hour even when i plays music windows media player says it cannot play and asks for web help.. even other apps say the same.. if i play any video there will not be any sound ,,... but if i restart my laptop then sound works properly and after a half an hour same issue repeats..plzz any one help me
my laptop:
Sony Vaio F15212
intel i3,500gb,
graphics:intel hd4000
WINDOWS 8..
plzz any one find a solution for me.. thank u.