I've heard (no pun intended) some claims that some storefronts in shopping malls play a noise that sounds like a mosquito, which apparently can't be heard by adults yet drives teenagers nuts. The purpose of this noise is to keep teenagers from loitering at the storefront's entrance.
I've heard a few of these noises on YouTube. However, every single one of these sound clips are perfectly audible to me. Better still, they don't really bother me at all.
I guess I'm skeptical because the majority of these stores have employees who would be painfully affected by his noise.
So is it true that stores have used such a noise and is it effective?