Controlling Sound

Acoustical engineers study sound and design headphones that reflect and absorb sound to protect against hearing damage. In this activity, students are acting as acoustical engineers as they design headphones using sound-absorbing materials. Engineers use the engineering design process to design prototypes which students will have the opportunity to do in today's activity. 

After this activity, students should be able to:

• Explain that some materials absorb sound, while others reflect it.
• Apply the engineering design process to design and test headphones that absorb sound.

Sometimes being in a rock band can be pretty fun, and other times all of the loud noise can take a toll on your body! A one-time exposure to extremely loud sounds or listening to loud sounds for a long time can cause hearing loss. The band “The Enginerz” has hired your team as acoustical engineers to design a pair of noise-cancelling headphones so that they can continue to jam safely on stage without hurting their ears! The band will choose their new headphones based on the best looking, the best feeling, and the best noise reduction (blocks the most sound).

The bandmates have agreed upon a budget of $50 to spend for each pair of headphones. Your team can spend less money than this, however, you cannot spend more. Since your team cannot afford all the materials, make sure to choose wisely! Also, the band doesn’t want to give up style for safety so make sure your team’s design rocks!

Background

In this activity, students need to use substances that absorb sound. Materials that absorb sound send back few or no sound reflections or echoes. These types of materials can be found in classrooms, offices and other places to help reduce sound.

Review the engineering design process.

The engineering design process.CopyrightCopyright TeachEngineering.org

Before the Activity

• Gather materials
• Make copies of the Headphone Design Planning Sheet (PDF) (one per group, or one per student if working individually)
• It may be helpful to set up several "construction stations" on various desks throughout the room so that the students can easily access the materials

With the Students

1. Divide class into teams.
2. In their teams, have students do the pre-activity to try out regular headphones to get an idea of what they will need to build.

Hearing Test:

Have students use their thumb to indicate what they are hearing with the headphones on: 

• • Thumbs up if they hear a sound clearly
  • Thumbs held halfway if they can kind of hear sound
  • Thumbs down whenever they do not hear a sound

https://www.youtube.com/watch?v=0VpI_2DTQhY

3. Hand out the Headphone Design Planning Sheet (PDF) to each student.
4. Students should review the engineering challenge and the design criteria and constraints. Students then work as a team to brainstorm ideas and generate multiple possible solutions. Students should review the Materials list and the cost of each material to stay within the budget. Make sure students discuss what materials they are going to use and why. 
5. Ask students to select the most promising solution and then draw their design on the Headphone Design Planning Sheet (PDF) (keeping within the $50 budget). Encourage students to make their design as detailed as possible.
6. Remind teams to get their design drawing and materials list checked off before beginning to build.
7. Give students time to build their design as a team.
8. Teams should test their headphones to see how they work, by using computer generated sounds (or buzzers, bells, etc.). Using a classroom speaker, teams can test their headphone design all at once, if preferred.

Rock n’ Roll Sound Check:

Start with no volume and very slowly increase the volume and stop as soon as the student wearing headphones raises their hand indicating that they can hear the music.

Song 1: https://www.youtube.com/watch?v=5XfRjVo5wOE

Song 2: https://www.youtube.com/watch?v=CQ0ftoiIQxU

Song 3: https://www.youtube.com/watch?v=2KGe_4leh_Y

9. Teams may iterate on their headphone design after testing and re-test.
10. Encourage students to try each other's headphones, and talk with each other about designs and materials that work well at absorbing sound.
11. Have a class discussion about the teams’ headphone designs. Which ones worked best and why? Discuss how engineers design, then build, and finally test their ideas. Engineers often have to redesign, rebuild and retest many times before they perfect their creation.

Pre-Activity Assessment

Absorb or Reflect?: Make a list on the board of materials that reflect sound and another list of materials that absorb it. Tell the students that today they are going to be using absorbent materials to create headphones that absorb sound. When would we want to use materials that reflect sound? (Answer: When we want something to be very loud, such as cymbals or bells).

Activity Embedded Assessment

Engineering Design Check-off: Since students need to get their designs checked off, use this time to talk with them about the features of their designs. Encourage students to add as many details to their designs as possible, including labeling the various parts. Have students discuss why they chose the materials they did. Make sure that students understand they are using materials that absorb sound. 

Post-Activity Assessment

Best Features: As a class, talk about which features of the various headphones worked the best and why. Review how these absorbent materials "soak up" or absorb sounds (soft, squishy, & sponge like materials absorb sound (sound decreases) while hard, dense, & thin materials reflect sound (sound “bounces”)).

Making Sense: Have students reflect about what they explored and/or the science and engineering skills they used by completing the Making Sense Assessment (PDF).

Assist students with scissors as needed.

Be sure to encourage students to periodically test their headphones as they build. If time allows, let students redesign and rebuild their headphones in order to make them even better.