Sound Waves - Part 2 Intensity

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SWBAT identify sounds that can cause permanent hearing damage in humans.

Big Idea

In this lesson, students will explore sound intensity and discover that sounds are measured in decibels.

Engage and Explain

25 minutes

I begin this lesson by showing this fun sound video from Bill Nye the Science Guy.   One of the reasons I chose this video to begin this lesson is because it has a nice balance of review material about waves that have previously been presented in lessons as well as new information.  In previous lessons, students have learned about different types of waves and examples of these type of waves.  Students have investigated light waves and sound waves. 


Explore and Elaborate

20 minutes

After the video I ask students if they have ever heard a sound that was so loud that they had to cover their ears? I lead a brief discussion about why they covered their ears.  

I tell students that without thinking about it, you covered your ears to protect them from the damage of loud sounds. Knowing that loud sounds can damage hearing is important in preventing hearing loss and deafness. Short exposure to sounds that are extremely loud can cause pain or even damage hearing, while long exposure to loud sounds can have the same affect.

 From the video, I remind students that the loudness of sound is measured in something called decibels. There is a wide range of sound decibels, but humans can hear in a range from 0 dB (called the Threshold of Hearing, or how soft a sound can be) to over 130 dB (called the Threshold of Pain, because it actually hurts your ears). Because of the large difference in noise between a whisper and a jet engine, each decibel level represents an increase of ten times the previous number. That means that a decibel level of 20 is ten times louder than a level of a 10. A decibel level of 30 is ten times louder than a 20, or one hundred times louder than a 10.

How do we protect our ears from the loud sounds that can cause hearing problems? While it's true that engineers often make the devices that are loud enough to damage ears, they also work to help protect people from hearing loss or injury. There are engineers that specifically work on acoustics or how sounds are heard and how to protect people from the dangerous sound levels. Engineers have created technologies for eliminating some sound from noisy rooms or areas, such as sound barriers around airports or busy roads. Engineers also develop the technology to help people who already have some hearing loss, such as hearing aids, cochlear implants, and replacing part of the bones in the middle ear with wires.

Next I present directions for an activity in order for students to learn about decibels and the loudness of sound.  

I give 10 students a "sound" (a piece of paper with the name of a sound prepared ahead of time; the decibel level for the sound is color coded and covered with a piece of paper.)

Next, I explain that the class is going to arrange the students at the front of the class in a "Sound Line" from softest sound to loudest sound.

When the class has arranged the students, have them guess the approximate decibel level of each sound.

When the class is sure they have the sounds in order, students remove the covering on the decibel level to see if they are correct.

If the students are not correctly arranged, they rearrange themselves.

In these videos, you can see students ordering the sounds. Notice how they give reasons and support when arranging the sounds. 





10 minutes
For this lesson I use informal formative assessment during the lesson. During the sounds sort activity, I ask students to name some sounds that are dangerous for your hearing. I also ask what kind of precautions students can take to prevent hearing loss?
I ask these questions to students to further support that science is about making sense of the world and understanding the world.  These questions support that scientists help solve problems by making sense of information and asking questions.