Pitch and Amplitude

Lesson Plan - Get It!

Audio:

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. Point to 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?

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?

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. Then, read the short article, The Pitch of Sounds (Encyclopedia Britannica Kids). Create your own definition to describe pitch.

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?

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.

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