High school science, special ed edition. We were reading a chapter on sound.
We had a whole period, and just reading gets a bit tedious, so to break things up I searched for videos demonstrating sound waves. In the limited time, I came up empty, but I did find this article on sounds only young people can hear.
Oooh, I had to try this.
I played the 8000 Hz. Then, the 12,000 Hz wasn't working in the article, so I found another on YouTube. We could all hear those. As I am over 40, the 15,000 Hz was inaudible to me and the instructional aide. The kiddos said they heard it fine. (They complained that it was irritating, though.)
And then I played the 17,400 Hz...
"Wait. I can't hear that! Are you playing something?"
I've had Josephine Joe in several classes. (You are probably aware I don't use students' actual names, and I haven't here. But I remember her because her first name is the feminine version that shortens to the male name that is her last name.) She hasn't made the blog before.
Everyone else in class heard it. They didn't much like it. One girl said it was giving her a headache.
I tried to calm Josephine down. In the previous class, there was one boy who didn't hear that tone either. He freely admitted that he plays his music on his earbuds way too loud. So, I assumed it was something like that.
Once Josephine was calm, I read that that was the frequency heard by only those under 18.
"Oh, okay then. I'm 19..."
(Before you question why a 19-year-old is still in high school, recall that this is a special ed class. They give those students a bit more leeway in completing their graduation requirements.)
She then proceeded to tell me how she was planning to see her doctor over not hearing that tone. She thought she was losing her hearing. She was so relieved to learn that she was normal.
Those tones worked perfectly at school, but when I tried listening to them on my home computer, there was some weird static. If you have similar issues, just go to YouTube and search the various frequencies. They have several videos with them.