I was at my Dad’s house the other day. We walked into his bedroom to get something, and a loud, high-pitched noise hit my ears. When I asked Dad about it, he had no idea what I was talking about.
My siblings could hear it from the hallway, but my dad and step-mom were oblivious. It’d probably been going on for days or weeks and they didn’t notice.
You may have heard about the “mosquito,” a device that blasts a very loud, very high-pitched sound in order to get rid of loitering teens. People over 30 or so don’t really hear it, but it annoys the kids.
So then kids got hold of it and created a mosquito alert for their phones. Now they can get text messages in class, and most of their teachers won’t hear the alerts. [Link]
Test your own ears and see how old you are:
I ran these by my three-year-old who liked them all. My wife hears up to about 16 or 17KHz. I can’t hear much over 14KHz.