Sound Teacher Guide




Physical Science

Grade Level


Activity Name(s)

Complex Sounds and Instruments

How Loud, How High?

Being Prepared

Be sure to run the sound grapher model on the computers that you intend to use with the class. Some computers may require particular settings and/or downloads prior to being used.

Set up the activities using the sound grapher far enough apart to minimize the interference of noise from one group to the next.

Getting Started

You will be using the Sound Grapher Model in each activity. Make sure you run this model prior to lesson to ensure all support software is loaded. Also, remind the students to choose the necessary settings prior to starting the data collection.

Suggested Timeline

Each lesson (How Loud, How High? & Complex Sounds and Instruments) can be completed in one class period. If your class period is less than an hour, you may have to allow extra time to get sufficient answers for the analysis questions and/or complete further investigations.

Thinking about the Discovery Questions

This unit is motivated by the discovery questions

In this lesson, the students are going to look at the transfer of sound energy and observe various properties of sound. As students use the sound grapher model, they will specifically look at the frequency, amplitude, and intensity of sounds and compare the sounds of various voices/instruments. They should look for trends and patterns in the data to draw conclusions on how they are related. Students will also think about the molecular particles and their role in sound transfer.

Energy is the ability to do work, and transferred anytime that work is used to move something against a force.


A common misconception that students have about energy transfer is: When one object pushes or pulls on another object, a force, not energy, is transferred.

Learning Objectives

Discussion: Setting the Stage

Discussion: Formative Questions

Discussion: Wrapping Up

Additional Background

Sounds heard occur because mechanical energy produced by the medium was transferred to the ear through the movement of atomic particles. Sound is a pressure disturbance that moves through a medium in the form of mechanical waves. When a force is exerted on an atom, it moves from its rest or equilibrium position and exerts a force on the adjacent particles. These adjacent particles are moved from their rest position and this continues throughout the medium. This transfer of energy from one particle to the next is how sound travels through a medium. The words "mechanical wave" are used to describe the distribution of energy through a medium by the transfer of energy from one particle to the next.

Waves of sound energy move outward in all directions from the source. Your vocal chords and the strings on a guitar are both sources which vibrate to produce sound waves. Without energy, there would be no sound.

Sound or pressure waves are made up of compressions and rarefactions. Compression happens when particles are forced, or pressed, together. Rarefaction is just the opposite, it occurs when particles are given extra space and allowed to expand. Remember that sound is a type of kinetic energy. As the particles are moved from their rest position, they exert a force of the adjacent particles and pass the kinetic energy. Thus sound energy travels outward from the source.

Sound travels through various mediums such as air, water, or solids. Sound does not travel when a medium is absent because there are no particles to carry the sound waves. The word "particle" suggests a tiny concentration of matter capable of transmitting energy which can be an atom or molecule. Sound does not travel in space because it does not have an atmosphere, leaving too few atomic particles to transfer the sound energy.


Complex Sounds and Instruments

  1. Can you say that each vowel has a unique "signature" that makes it different from the others, regardless of who spoke it?

    Timbre is the combination of qualities of a sound that distinguishes it from other sounds of the same pitch and volume. Students should use their data to support their answers, but reference the unique properties identified.

  2. Can you recognize this signature in both the "waves" mode and the "frequency" mode?

    Yes, unique properties should be noted in either setting.

  3. What is the difference in timbre between a female and a male voice?

    Note: frequency or pitch is not the question here. (Answers will vary, but should support data and compare the unique properties.)

  4. Does each instrument have a unique signature (timbre) that is recognizable in both the waves and the frequencies mode?

    Yes, the timbre of an instrument is what makes it unique. A piano and guitar will produce a unique sound even when playing the same pitch at the same loudness.

  5. Describe the difference, in terms of mix of frequencies, between a "pleasant" sound and an "unpleasant" sound.

    Students may have different opinions on what should be described as "pleasant" or "unpleasant" sounds, but should note similarities in data of each sound. High frequencies produce high pitch sounds.

  6. For each instrument that you tested, describe:

    Answers will vary, although students should note that:

How Loud, How High?

  1. Look at the graph of a combined hum and whistle. The graph represents 30 milliseconds (0.030 seconds) of time. Count how many cycles occur in that time for each pitch. Calculate the time for one cycle for each pitch. This is called the period, measured in seconds.

    Answers will vary depending on the pitches of the hum and whistle.

  2. If you know the time for one cycle, you can calculate how many cycles occur in one second. Explain how you made this calculation. This is the frequency, measured in cycles per second.

    Frequency = Cycles / 0.03 seconds

  3. The speed of sound in air is about 340 m/s. How far (in meters) does the sound travel in 30 ms?

    340 m * 0.03 s

  4. For each pitch, how far (in meters) does the sound travel during one cycle ? This is the wavelength of that sound.

    Answers will vary depending on the low and high pitches that the students could make. Calculation should be completed as in question 3.

Further Investigation

Additional materials will be needed to construct an instrument. Make sure the students understand the difference between pitch, loudness, amplitude, and frequency of sounds by testing their instruments with the CC Sound Grapher.