I don't really care if people hear me pee - I do pee around the edge of the bowl because I believe that's courteous, but if somebody hears me do it, oh well. I also don't care about hearing other people pee. If you've gone to the toilet, it's for one of three things, and each has a very distinctive noise. I'd be worried hearing nothing from someone in the bathroom. They might have had a heart attack and died.