Instructor: Hi class, can anyone tell me what sound is? Boy 1: Sound is music.
Instructor: Sound is music. Boy 2: Sound is energy.
Instructor: Sound is energy. Girl: Sound is waves.
Instructor: Sound is waves. Good, these are all really good examples. So, sound is energy, like light or electricity. Sound is made when objects vibrate. Sound vibrations travel in waves by pushing air molecules together. Vibrations can be very powerful. The stronger the vibrations, the louder the sound. And we measure sounds in decibels. So, in order to learn how sound can damage our hearing, let’s first talk about how we hear. So, sound waves travel into the outer ear, which funnels them into the ear canal and sends them to the eardrum. The eardrum then vibrates and sends that vibration to three tiniest bones in the body— the malleus, incus, and stapes. These three bones vibrate to amplify, or increase, the sound and send that vibration into the cochlea, this snail-shaped organ here. The cochlea is filled with liquid and 18,000 tiny hair cells. So, how do you guys think that sound damages our hearing? Boy 1: The bones in your ear vibrate too much. Instructor: Good, well that is possible. The most common cause of hearing loss is damage to the hair cells. So, this is a picture of a hair cell. So, the green part of this image is the actual hair cell, and the tiny hair-like structures on top are called the hair cell bundle. Now, we need to mention that these aren’t
like the hair on our head, but they’re called hair cells because these are hair-like structures. They lay in the liquid portion of the cochlea, and when sound vibrations move through the cochlea, they bend the hair cells. And when they bend, that sends an electrical signal to the brain so that we can hear. So, let’s do a little activity to show how hair cells work. So, everyone grab your pipe cleaners. Alright, your fist will be the hair cell, the pipe cleaners will be the hair cell bundle, and your hand will be the sound wave, ok? So, let’s say we’re having a nice, light conversation in the library. Nice and quiet. Good, gentle bending. Then we go out to recess, and it’s a little louder. Good. Now we go to your cafeteria. Everyone is having fun and screaming a little bit. Then you go out to the fireworks where it’s BING, BANG, BOOM! Look at your hair cell bundle. So, now these are your damaged hair cells. So, look at your hair cell bundle. Can you fix it? Can’t do it, can you? It’s not working. So, when your hair cells are damaged in your ear, it works the same way. Once these hair cells are damaged, they can’t be repaired. Currently, only fish, birds, and frogs can regrow their hair cells. Scientists are currently trying to figure
out how to recreate this phenomenon in humans so that we can regrow our hair cells. Now we know what sound is, how we hear, and how sound can damage our hearing. Announcer: This demonstration was brought to you by It’s a Noisy Planet. Protect Their Hearing.®, a public education campaign of the National Institute on Deafness and Other Communication Disorders, part of the National Institutes of Health. The Noisy Planet program is designed to increase awareness among children ages 8 to 12, their parents, teachers, and others about the causes and prevention of noise-induced hearing loss. Noise-induced hearing loss can build over time and is permanent, but it can be prevented. Noisy Planet reminds you to lower the volume, move away from the noise, and wear hearing protectors such as earplugs or earmuffs. For free resources, including educational tips and tools for parents and teachers, as well as pop quizzes and fun, educational games for preteens, please visit www.noisyplanet.nidcd.nih.gov, or email us at [email protected]