Crackling audio on 2013 MacBook Air?

The speakers on my MacBook Air seem to work fine when playing things through iTunes or YouTube, but on certain websites the audio seems to crackle, and it is getting very annoying. I've had the computer for about two months, and the speakers were fine in the beginning. Could it be a software issue? I've had about three Lion updates since I purchased it. I don't really believe it's a hardware issue because it plays absolutely fine on certain websites, but on Tumblr especially, the audio crackles and pops. Any help??

Thanks!!