Many people lose their ability to hear high-frequency sound as they age. You may have heard about the British company that was using high-frequency sounds to drive off loitering teens - the sounds apparently sound incredibly shrill. I say apparently" because "this page lets you test your "auditory age" and my aged ears couldn't hear the tone at all.
The rest of the story is also fun: some kids converted the tone into a cellphone ringtone that they could use in school and other illicit venues without the adults knowing. The kids in one school were busted when a 24-year-old teacher heard the ringtone.
A story about an Oregon man who citizen-arrested a policeman for parking illegally
You've probably heard about the guys on Japanese subways whose job it is to cram people into crowded subway cars . If you haven't actually watched it happen, you're missing something. It's much weirder than you might imagine.