It would probably just make the most sense to have a mute button on each individual game page, so that the noise would be blocked out. Or, they could just remove the sound of the sword intro.
i have a volume mixer where i can adjust the sound volumes on individual programs such as windows media player being at one level, Mozilla at another and internet explorer at a different one, maybe you should consider looking into one of these.
How hard is it to include a mute button?
We have several people sharing the same computer and you have to close someone's game if you need to hear something on another page.