I did not get the effect I wanted, because this extension does not work with the language learning site Duolingo. It can only work with Facebook, HTML5. That's why my neighbours had to listen to people shouting in Spanish while there were quiet sounds of nature playing in the background. p.s. yes, default volume 100% please, not 10%. Somebody, please, make an extension which can change volume for any tab and any sound source, not only HTML5.