The Properties of Sound Waves

Lesson Plan

 

State Standards:

4.1 Describe the measurable properties of waves (velocity, frequency, wavelength, amplitude, period) and explain the relationships among them.

Essential Question:

How do you create different sounds with vibrating strings?

Lesson Question:

Introduction:

Blue Man Group

Like a member of The Blue Man Group, you are visiting from another galaxy and find yourself at a concert where musicians are playing various stringed instruments (Bass, cello, violin, viola, guitar etc.) You are mesmerized by what you hear. Why do the sounds produced by the cello sound so different from the sounds produced by the viola? How does each musician make so many different sounds come from the same instrument? How can you figure out how these string instruments work?


Like a Blue Man, you are going to answer these questions by exploring the world around you.

Task:

You will investigate how string length and tension affect the frequency of a sound wave, as well as what affects amplitude. You will start by examining terms and misconceptions, then engage with a simulation. Then you will experiment with your own stringed instrument to discover what you can about the properties of sound waves. To summarize your experience, you will post your findings to the class Wiki discussion.

Lesson Experiences:

I. Elicit:
A. Let's talk about terminology and prior knowledge / misconceptions.

  1. In small groups, build the waves cube ( waves cube worksheet ).
  2. Read the science words on the box.
  3. Discuss the meanings of the words that are familiar and try to make connections between the words.
  4. Report back to the class what your group believes is the word on the bottom of the box and what evidence you have to support this belief.
  5. Discuss with your teacher what the answer is.


B. Now let's clear up common misconceptions by participating in a simulation.

simulation screenshot

  1. Go to the website: Classzone Frequency and Amplitude Simulation
  2. Begin with both the frequency and amplitude set at the lowest setting and press GO.
    • Change the frequency to a higher setting, press Go and record how the wave has changed in lab manual.
    • Change amplitude to a higher setting, press go, and note how the wave has changed in lab manual.
  3. What happens as you adjust the settings?
  4. Recap as a class -- describe in your own words:
    • What is frequency?
    • What is amplitude?
    • How does frequency relate to a sound wave? What is another word for the frequency of a sound wave?
    • How does amplitude relate to a sound wave? What is another word for the amplitude of a sound wave?

II. Explore • Explain • Elaborate • Extend • Evaluate

Now we'll work to discover more about sound waves. Here are the steps:

  1. Work in groups of three, mount a pulley to one side of the lab table and a clamp directly opposite the pulley on the other side of the table.
  2. Then tie one end of the string to the clamp. The other end of the string will be tied to the 500 gram mass. The string will next be extended over the pulley, allowing the mass to hang over the table.
  3. Place a styrofoam cup under the string, near the clamp, allowing the string to vibrate freely without hitting the table.
  4. Pluck the string, listen to the sound, and observe the string vibrate. Measure the length of the vibrating string.
  5. Make a table in your journal to record length of vibrating string; load on mass hanger; and pitch (high, medium or low). Record their observations from step 4 in your table.
  6. Change the length of the section of vibrating string by sliding the cup, measure the length of vibrating string, pluck the string and record their observations in the table. Repeat this step several times varying the length of vibrating string. Note each of these in your journal.
  7. As a group record a general statement regarding the relationship between pitch / frequency and string length in each of your journals.
  8. Now explore how mass affects pitch / frequency. Keeping vibrating string length constant, add mass in 500g increments, each time plucking the string and recording the change in pitch / frequency, until a mass of 2,000g has been reached. Note each of these in your journal.
  9. As a group record a general statement regarding the relationship between mass/tension and pitch / frequency and record it in each of your journals.
  10. Discuss the relationships between length and frequency and tension and frequency as a class with each group presenting their findings and generalizations.

Blue Man Group

Homework:

Image you are a “Blue Man” (a visiting alien). Post to the class Wiki page your answer to this question:

“How does what you have learned in the investigation apply to the playing of a guitar?”

Include in your post answers to the following questions:

Remember to maintain your perspective of a visiting alien, but make sure that English-speaking Earth people can read and understand what you write!

Conclusion:

Now you understand the properties of sound waves and what factors affect these properties, and will be able to apply their understanding to the playing of a stringed instrument. Imagine what you could do if you joined the Blue Man Group!

Assessments:

You will be assessed on your observations posted to the class Wiki.

Areas of Understanding:

Strong

Good

Adequate

Inadequate

Weight:

String Length

Demonstrates a deep understanding of the affect of string length on frequency.

Demonstrates adequate understanding of the affect of string length on frequency.

Demonstrates limited understanding of the affect of string length on frequency.

Did not demonstrate any understanding of string length on frequency.

Tension

Demonstrates a deep understanding of the affect of tension on frequency.

Demonstrates adequate understanding of the affect of tension on frequency.

Demonstrates limited understanding of the affect of tension on frequency.

Did not demonstrate any understanding of tension on frequency.

Amplitude

Demonstrates a deep understanding of how to affect change in amplitude.

Demonstrates adequate understanding of how to affect change in amplitude.

Demonstrates limited understanding of how to affect change in amplitude.

Did not demonstrate any understanding of how to affect change in amplitude.

Creativity and Perspective

Post was extremely creative and was written from the perspective of a visiting alien.

Post was somewhat creative and was written from the perspective of a visiting alien.

Post was not very creative but was written from perspective of a visiting alien.

Post was not creative at all and was not written from perspective of a visiting alien.

Spelling and Grammar

Post was clear and contained no spelling or grammatical errors.

Post was clear and had few spelling or grammatical errors.

Post was not clear and contained few spelling or grammatical errors.

Post was unclear and contained many spelling and grammatical errors.

 

Resources:

Eisenkraft, Arthur. Active physics A Project-Based Inquiry Approach . 3rd ed. New York: Te Herff Jones Company, 2010. pp. 484-486 and pp. 508-510. Print
Classzone.com

What's in a Word? How Word Choice Can Develop (Mis)conceptions About the Nature of Science ( Download PDF 266KB ) by Renee Schwartz.

Materials:

Teacher Notes:

Students will be placed into groups of 2-3 for the vibrating string investigation, but will complete the homework assignment individually so that whether each student understood the concepts of the investigation may be accurately assessed.