By the way, just a comment:  I find it strange that you chose the "Video" options page to contain this feature.  Intuitively, I went first to "Text & Speech" options page, and not finding it there, then to the "Sound" options page.  It never occurred to me to look in the "Video" options.

Perhaps that was your intent, to bury the feature to avoid it being triggered inadvertently or found casually by children?

  -dZ.