I get the impression that that hissing noise is mostly a British  thing. Although it is possible i have heard that  white noise here in the Netherlands  too, but it is definitely not standard.  As the trash truck still beeps..,(reply>), Not sure its a good thing to change. I mean: Hey a beep i know what to do! or : Hey something is hissing, some air is escaping somewhere. Well it has nothing to do with me, splut.