SummaryTo further their understanding of sound energy, students identify the different pitches and frequencies created by a vibrating ruler and a straw kazoo. They create high- and low-pitch sound waves.
Electrical engineers understand sound energy as part of the electronic devices and tools they design, such as iPods, radios, test equipment, medical equipment and sonar. Often, they design equipment that can "hear" ultrasound and infrasonic sounds not detectable with human hearing. Ultrasound can test metals and plastics in manufactured equipment for tiny flaws and cracks that indicate product weaknesses. They also design medical equipment that uses ultrasound to diagnose unseen body conditions or injury. Acoustics engineers are specialists in noise control and acoustic design in a given space or structure, such as auditoriums, airports or art galleries. Audio (or sound) engineers work in multimedia, generating and broadcasting sounds mechanically.
After this activity, students should be able to:
- Define pitch and frequency.
- Describe a sound with a high or low pitch and frequency.
- Describe how to change the pitch of a sound.
- Give an example how engineers use pitch and frequency in the design of new products.
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Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.
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Each group needs:
- plastic drinking straw
- Pitch and Frequency Worksheet, one per student
What is sound energy? It is the energy produced when sound is created. Today we are going to talk mainly about two characteristics of sound energy, pitch and frequency. Everyone: Create a sound, any sound. Can you hear higher or lower sounds around the room? This characteristic of sound is called pitch. What is a frequency? The number of vibrations for each sound pitch is called its frequency. High-pitched sounds have faster frequencies or more vibrations than low-pitched sounds with slow frequencies.
How do we use sound? We use sound to communicate, give warnings, talk to each other and send messages to our friends over the telephone. We also use sounds to entertain us and help us relax or get energized when we listen to music. Engineers also listen to sounds and create machines that detect sounds that our ears cannot even hear! Our ears pick up a wide range of frequencies. However, some animals hear frequencies that are too high-pitched or low-pitched for human hearing. These frequencies are called ultrasounds and infrasonic sounds.
Engineers have designed instruments that "listen" to ultrasound and infrasonic sounds. Ultrasound can detect tiny flaws in metals, plastics and other materials used to make parts and components. Being able to detect these tiny flaws helps keep damaged products from being sold to us in stores. Who would want to use a jet, car or a bicycle with tiny cracks in it? Every time something is cracked, it weakens the overall strength of the item and eventually it may break.
Engineers design other instruments that take pitch and frequency in consideration. Ultrasound is used a lot in medical equipment, especially in devices that help us view what we cannot normally see. These medical instruments help a basketball player see if his ankle injury is going to keep him out of the rest of the game or allow an EMT to see inside a person's injury in a car-wreck. NASA engineers are developing medical instruments that help people diagnose injuries in space.
Today, we are going to look at sound energy and how changing the length of an object changes its pitch and frequency. Are you ready to make some noise?
frequency: The rate of vibrations in different pitches.
infrasonic sound: Sound waves or vibrations with frequencies below that of audible sound (too low for human hearing).
kazoo: A toy musical instrument with a membrane that produces a buzzing sound when a player hums or sings into the mouthpiece.
pitch: The highness or lowness of a sound.
sound energy: Audible energy that is released when you talk, play musical instruments or slam a door.
sound wave: A longitudinal pressure wave of audible or inaudible sound.
ultrasound: Sound waves or vibrations with frequencies above that of audible sound (too high for human hearing).
vibration: When something moves back and forth, it is said to vibrate. Sound is made by vibrations that are usually too fast to see.
volume: When sound becomes louder or softer.
wave: A disturbance that travels through a medium, such as air or water.
Before the Activity
- Gather materials and make copies of the Pitch and Frequency Worksheet.
- Divide the class into teams of two students each.
With the Students: Ruler Experiment
- Have students hold the end of a ruler flat against a table and hit the other end, which extends beyond the edge of the table.
- Repeat this action several times, pulling more of the ruler onto the table each time.
- Ask the students how changing the length of the portion of the ruler that hangs past the table changes the vibrations in the ruler. How does it affect the pitch and frequency of the sound the ruler makes? (Answer: The longer the amount of the ruler beyond the table edge, the lower the pitch and frequency.)
- To add a math component, have students record on the worksheet how long the ruler vibrates at different lengths and graph the results on the worksheet.
With the Students: Straw Kazoo Activity
- Make a straw kazoo by cutting one end of a straw to a point.
- Blow into the straw and then cut a bit off the other end to make it a shorter kazoo.
- Observe the change in pitch as the straw kazoo is shortened.
- Discuss observations: Recall that pitch is the highness or lowness of a sound, and frequency is a pitch's rate of vibrations. What type of pitch is characterized by slower vibrations? (Answer: A low pitch.) What type of pitch is characterized by faster vibrations? (Answer: A high pitch.)
Remind the students to hold on to the rulers tightly so that they do not accidentally fly across the room when they are struck.
This activity can be noisy. Consider having the students work in groups outside of the classroom to minimize the sound (!) disturbance to other classrooms.
Brainstorming: As a class, have the students engage in open discussion. Remind them that in brainstorming, no idea or suggestion is "silly." All ideas should be respectfully heard. Take an uncritical position, encourage wild ideas and discourage criticism of ideas. Ask the students:
- What can you think of that makes noise?
- What is different and similar between all these noises?
- Pick two or three of these noises and draw a Venn diagram on the board to compare and contrast them. (Note: A Venn diagram uses circles to represent sets, with the position and overlap of the circles indicating relationships between the sets.)
Activity Embedded Assessment
Observations: Have the students write down their observations of the ruler experiment and the kazoo activity. Compare their observations with a neighbor (not a person on their team) and identify similar and dissimilar observations. Have each group report their findings to the class.
Pitch It: Go around the room and have each student identify a low-pitch noise or a high-pitch noise and say whether or not the sound waves are traveling faster or slower that the sound identified by the previous student. For example: Student 1: Drum — Low pitch; Student 2: Flute — High pitch waves travel faster than the drum sound waves; Student 3: Dog growl — Low pitch waves travel slower than the flute sound waves, etc.
Kazoo Hullabaloo: Tell the students that they are engineers trying to design the perfect kazoo. Give student groups of three or four new straws and have them design and re-design their kazoo until they have four different pitches, each one that is a slightly higher pitch that the person next to them! How can you tell the kazoos apart? (Answer: The shortest kazoo has the highest pitch.) Is there anything they could do to make the kazoo better still? How about poking little holes in the side and playing it like a recorder? Have the students create a jingle that uses the kazoos and communicates to the audience how a kazoo works.
Have students make a variety of simple instruments (see ideas in Sound Lab: Simple Instruments). Have each student explain how their instruments make the sounds and why. Conclude by having students use their instruments to perform a song. If the activity leaves the students with a desire to make some more high- or low-pitch sounds, take them to the music room to learn about the pitch of piano notes. For example, the note of middle C, in the middle of a piano keyboard, has a frequency of 261 Hz. The length of this note's sound wave is 126 cm (49.6 inches).
For younger students, remove math component by eliminating the Pitch and Frequency Worksheet.
Audio Engineering Society. Audio Engineering Society, Inc., New York, NY. Accessed October 3, 2005. http://www.aes.org/
Audio Engineering, The Pre-Engineering Times. Published November 2004, Issue #34. JETS, Your Pathway to Careers in Engineering, Alexandria, VA. Accessed October 3, 2005. (Description of audio engineering careers) http://www.jets.org/newsletter/1104/feature.htm
Dictionary.com. Lexico Publishing Group, LLC. Accessed December 19, 2005. (Source of some vocabulary definitions, with some adaptation.) http://www.dictionary.com
ContributorsSharon Perez; Natalie Mach; Malinda Schaefer Zarske; Denise W. Carlson
Copyright© 2005 by Regents of the University of Colorado
Supporting ProgramIntegrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
The contents of this digital library curriculum were developed under grants from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation (GK-12 grant no. 0338326). However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.
Last modified: March 16, 2018