Pitch and Amplitude

Contributor: Meghan Vestal. Lesson ID: 11475

We're going to pitch this lesson to you so you can learn about the volume of sounds and how frequency affects what you hear. Get a Slinky, a rubber band, and watch an amazing scientific music video!

categories

Physical Science

subject
Science
learning style
Auditory, Kinesthetic, Visual
personality style
Beaver
Grade Level
Middle School (6-8)
Lesson Type
Dig Deeper

Lesson Plan - Get It!

Audio:

These two images show different sound waves. What is the difference between the type of sounds being produced to create each sound wave?

Look at the two sound waves pictured above.

Write one or two sentences for each sound wave describing the type of sound you think each sound wave represents. Hold on to these sentences. You will check to see if you are correct at the end of this section.

In the last Related Lesson, found in the right-hand sidebar, you learned about the parts of a compression wave. Take a few minutes to review what you learned in that lesson, before moving forward with this lesson.

Look at the following sound wave. Show your teacher or parent a compression, rarefaction, crest, trough, and wavelength. Then, count the frequency (this picture represents one second). If you are unsure what any of these parts are, make sure to go back and review the previous lesson. You will need to know each of these parts to complete this lesson.

In this lesson, you will learn how pitch and amplitude are related to sound waves.

Pitch is determined by the frequency of a vibrating object. Objects vibrating quickly have a higher pitch than objects vibrating slowly. What type of sound do you think has a greater frequency: one with a high pitch or one with a low pitch? Tell your teacher or parent.

A sound with a high pitch is going to have a greater frequency than a sound with a low pitch.

What about wavelength? What type of sound do you think produces a larger wavelength? Tell your teacher or parent.

A sound with a low pitch creates a larger wavelength. The following compression waves will help you see the difference between a high pitch and a low pitch:

Compare and contrast the wavelengths with your teacher or parent. Then, read the short article, The Pitch of Sounds (Encyclopedia Britannica Kids). Create your own definition to describe pitch. Share your definition with a teacher or parent.

Amplitude describes the amount of energy, or force, in a compression wave. What type of sound would cause molecules to vibrate with a lot of force? Share your response with a teacher or parent.

Amplitude is directly related to volume. The greater the volume, the greater the force. When looking at a sound wave, the amplitude is displayed as the height of the wave from its resting position. The line that runs through the center of a wavelength is the wave's resting position.

Loud sounds produce higher waves because loud sounds have a greater amplitude. Low sounds produce shorter waves because low sounds have a smaller amplitude. Continue reading about amplitude on the BBC's Amplitude, wavelength and frequency. When you get to the bottom of the page, use the interactive to investigate what sound waves look like with different amplitudes, wavelengths, and frequencies.

Then, move on to the Got It? section to see how pitch and amplitude directly affect sound waves.

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