Complex Sounds and Instruments
How Loud, How High?
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.
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.
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.
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.
What words describe sound?
soft, loud, deep, high, frequency, pitch, volume, wavelength, waves, timbre, intensity, cycle, period, etc. (answers will vary)
Sound is vibration. What vibrates?
The molecular particles next to the object generating the sound.
Sound can be transmitted through the air and through solids. How does it travel from one place to another?
The vibrating particles have kinetic energy, which allow them to travel through various medium.
If you were near an explosion in outer space, would you hear it?
No, because outer space is a vacuum which does not contain the media needed to transfer the vibrations from one particle to the next.
Describe how sound is a transfer of energy.
Mechanical energy produces sound vibrations in the adjacent particles which travel to other particles transferring energy to each particle it contacts.
What is timbre?
Timbre is the combination of qualities of a sound that distinguishes it from other sounds of the same pitch and volume.
What is frequency and how is it perceived?
Frequency is the number of vibrations that an individual particle makes in a specific period of time, usually a second. Frequency refers to how often a wave passes through a certain point. Changes in frequency are perceived as changes in pitch, high frequency results in high pitch sounds.
What is amplitude?
Amplitude is the size of pressure variations which is a result of the measure of energy. The more energy a wave has, the higher its amplitude, which is measured as the wave height. As amplitude increases, intensity also increases.
What is intensity and how is it perceived?
The intensity is the amount of energy a sound has over an area. Sounds with a higher intensity are perceived as being louder.
What is energy?
Energy is the ability to do work, and work is moving something against a force. Energy can be found in a number of different forms.
How is energy transferred?
Energy can be transformed into another form of energy, but it cannot be created nor destroyed. Energy has always existed in one form or another. Energy transfer occurs as particles move.
How is sound energy generated and transferred?
Sound is generated when vibrations are produced in a medium. The vibrations have energy and transfer that energy as it comes in contact with other particles of matter. An example of sound energy and transfer: When you talk on the phone, your voice is transformed into electrical energy, which passes over wires (or is transmitted through the air). The phone on the other end changes the electrical energy into sound energy through the speaker.
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.
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.
Can you recognize this signature in both the "waves" mode and the "frequency" mode?
Yes, unique properties should be noted in either setting.
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.)
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.
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.
For each instrument that you tested, describe:
Answers will vary, although students should note that:
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.
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
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
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.
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.