loss of sound from internal speakers when playing games or videos

after about 10 -15 min playing online games or videos I lose sound from internal speakers.If I go in speaker settings and disable speakers and then inable speakers I have sound again but only lasts 10-15min.again and them no sound .I have to keep doing this over and over to get sound that only lasts for 10-15min. I have a toshiba laptop,Windows 7  I nternet explorer 9