How We Hear Classroom Demonstration: What Is Sound?
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How We Hear Classroom Demonstration: What Is Sound?

Instructor: Hi class, what comes to mind when you think about sound? Boy 1: Sound is music. Girl: Sound is waves. Boy 2: Sound is energy. Instructor: Very good. Those are all great examples. So, what is sound exactly? 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 powerful. The stronger the vibrations, the louder the sound. And sound is measured in decibels. So, this is a diagram of the ear. And in this diagram, it’s broken up into three different parts— the outer ear, middle ear, and inner ear. So, I want you to think about the sound that a trumpet makes. So, a trumpet makes a sound. And those sound waves travel, starting from the outer ear, and gets funnelled into the narrow passageway called the ear canal, until it reaches the eardrum, which then causes the eardrum to vibrate, which in turn, causes the three tiniest bones in the body to vibrate. And they increase and amplify the sound, so they’re called the malleus, incus, and stapes. So, those sound vibrations travel to the cochlea, the snail-shape organ in your inner ear, which is filled with fluid and teeny, tiny hair cells. So, the fluid in the cochlea ripples and causes a wave, and the hair cells get an electrical impulse, and then your auditory nerve sends a signal to the brain to hear. And that’s how we hear. And now I would like seven volunteers to act out this very important hearing process. Ok, one, two, three, four, five, six, seven. All of you can line up. All of you can line up over there. So, now that we learned how sound travels to the ear, we’ll have your classmates act out the parts of the ear for now. So, we’ll start with the noise source. [HORN SQUEAKS]
And then you’ll be the eardrum, so you’ll clap. And then you’re the malleus, so you vibrate. You’re the incus, so you vibrate. And you’re the stapes, so you vibrate. And you’re the cochlea, so you slosh. And you’re the brain, so you get the signal to hear the sound. So, now that you’ve practiced, let’s do it. And let’s remember it’s a chain reaction, and it happens really fast. [HORN SQUEAKS] Instructor: And that’s how we hear. Thank you, you guys did a great job. And now we know how we hear. 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, or email us at [email protected]

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