Illuminations: Do You Hear What I Hear?

Do You Hear What I Hear?

How do computers represent sound?

What is a sound wave? How can a sound wave be measured?

Frequently sound is described using terms such as pitch, tone, frequency, intensity or loudness. To understand the origins of these terms as well as to understand the mathematical models used to represent sound, this investigation can help you to explore the dynamics of a sound wave. The physical model has been simplified to highlight important scientific and mathematical features. Subsequent investigations will explore additional complexities of a sound wave.

The sound wave is controlled by two parameters: the amount of initial energy put into the string (initial displacement) and the amount of tension in the string. The animation of the string has been slowed down so that model of the wave can be observed clearly.

Learning Objectives
 

Students will

  • explore the dynamics of a sound wave

Materials
 
  • Computer and Internet connection

Instructional Plan

Activity

1. Use the Listen button to hear the sound for the current settings.

Use the sliders to adjust the two parameters.

How does each slider affect the sound that is produced?

2. Now turn on the animation of the sound wave using the START/STOP button.

What effect do the changes in the sound have on the animation of the string and the particles that you see?

How do these observations correspond to the observations from part 1?

3. Click on a single particle - its color should change to red. What is the motion of your particle?

4. Click on a second particle. How does the movement of this particle compare to the first particle?

5. Click and drag vertically on a column of particles. You may want to do this on more than one column.

What do you observe about the behavior of the column of points?



[Standalone version of the Sound Wave Applet]

Think About This

1. Watch the particles near the string. Why do you think the particles behave this way?

Given that the particles near the string are not attached to the string, why do you think the particles move to the left as the string moves to the left?

2. You may have observed that at times the particles are densely packed and at other times the particles are widely spaced. What physical quantity is used to describe this feature?

3. Describe situations in which sound waves are measured (recorded).

What do you think is the physical quantity being measured in each case?

NCTM Standards and Expectations
 
Data Analysis & Probability 9-12
  1. Compute basic statistics and understand the distinction between a statistic and a parameter.
  2. Understand the meaning of measurement data and categorical data, of univariate and bivariate data, and of the term variable.
  
1 period   

NCTM Resources

Navigating through Data in 9‑12

 Activities
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