One day, my sophomore year of high school, some of my classmates and I were exploring the idea about how adults cannot hear high frequencies like younger people can. We were in a huge debate, some believed it was true and some didn't. Then we decided to do an experiment on if our teachers could hear high pitched noises. One of my friends pulled up an app on his phone that made the high pitched sound and we started our experiment. First, we tested it on our English teacher, a middle aged man. During class, my friend turned on the app which resulted in other students wondering what that noise was, as my teacher continued on teaching. He did not hear a thing! Next, we tested it on our science teacher, who was pretty young. The teacher could start to hear something, but told us it was not very loud and distinct, while everyone could hear it perfectly. Lastly, we experimented on our health substitute, who was fairly old. It was more like a study hall, so everyone was silent. When my friend started the high pitched noise, all the other classmates sat and watched to see if our substitute would look up. She did not. Then one kid asked if she could hear anything, and she said no. From the three tests we performed that day, we came to the conclusion that it is true: As you get older, it is harder for you to hear high pitched noises. This also resulted in a discussion about how insanely high-pitched dog whistles are and how great dogs' hearing must be if humans cannot hear a sound. My friends and I still talk about that day and how we could honestly say we learned something.
My picture would not post, but here is the link: http://img.anongallery.org/img/2/6/hipster-dog-i-like-dog-whistles.jpg