Macbook sound problem?

I had my Macbook on the lowest volume and I was watching a video, then suddenly, out of nowhere, I started hearing a loud static noise. The sound was still playing but there was this awful static, so I restarted. When I turned it back on, the sound wasn't working at all and there was no static. After about ten minutes the static started again and with it, the sound was working again. Now, five minutes later, it's gone back to no static, and no sound. What's going on?!