Absorbing Airplane Noise!

Materials engineers develop, process, and test materials used to create many products. In airplane design, materials engineers select, test, and evaluate the material used in all parts of the aircraft, from the fuselage and wings to the wheels and engines. The inherent nature of aircraft design allows engineers in other fields to design and build machines, structures, or technology used to mitigate the negative effects of an airplane’s impact on the environment.

After this activity, students should be able to:

• Test a variety of materials to determine which absorbs sound the best.
• Understand and discuss what materials engineers do.
• Think and outline design iteration suggestions.
• Understand what the engineering design process is and why engineers use it.

Let us watch a video. Pay close attention to what is happening in the video. Afterwards, we will discuss any questions you may have.

[Show students the following video: “London Heathrow Plane Spotting” https://www.youtube.com/watch?v=iHVZ_Dlssec]

What did you notice about the video? What do you wonder? (Write students’ responses on the board. If the students do not notice it, direct their attention towards the video with the buildings in the background.) What is the problem with these buildings in the background of this video with the loud airplane flying close to it?

We have a problem for which we must engineer a solution: there is a school in a city that is located directly next to an airport. We have been asked to design model “buildings” that best keep out the sound of a jet engine so that they are not disturbed throughout the day. (Ask students if they have any questions about the problem.)

Before we begin, can anyone make sense of the word “insulation”? (Elicit student responses.) Insulation is material that is used to stop the passage of electricity, heat, or sound from one place to another. As we design our buildings, we must think about what materials will stop the passage of the sound of the airplanes to the schools’ classrooms the best.

We will be acting as materials engineers in this activity to solve this problem for other people. Can anyone tell me what they think materials engineers do? (Elicit student responses.) We will use the engineering design process to choose different materials and to design a model building that best keeps the sound out caused by the very loud plane engines.

CopyrightCopyright TeachEngineering.org, 2022.

Background

Sound is a type of energy made up of vibrations. Sound is created when a force causes an object or substance to vibrate. These vibrations are called sound waves, and they travel through the surrounding substance (such as air, water, or a solid) in a wave to our ears. Stronger vibrations will result in louder sounds; weaker vibrations make softer sounds.

Sound can be reflected or absorbed. Reflection is when sound waves encounter a material and bounce back. Think of an echo in a large hall or in a canyon, or even music in a concert venue. Absorption is when the sound waves hit a material and are taken up, like a sponge takes in water. Soft items such as carpet and curtains will help to absorb sound and make a room quieter. Sound absorption materials are often used for noise control, especially in buildings and rooms that are near loud noises.

Before the Activity

• Gather materials and make copies of the Design a Building Worksheet (PDF) (one for each student).
• • Pre-cut or size all the materials (for example, the pieces of cardboard / tape to a certain size / length). This will make it easier to “sell” materials to students.
• Download a sound app to a cell phone, computer, tablet or use a sound meter if you have one.
• Assign costs to each material and decide on a budget for each group. (For example, each group gets $20 to spend on their design and each material costs anywhere from $1.00 - $3.00.)
• Display the materials and costs to students in a common area. Example of costs:
• • $1 per piece of 15-cm by 15-cm cardboard
  • $1 per glue bottle
  • $2 per 30-cm of tape

With the Students

1. Divide the class into groups of three students.
2. Explain the problem the students are trying to solve. Use the EDP image in the Introduction/Motivation to walk the students through the seven steps of the engineering design process. Identifying the problem and engineering criteria and constraints is the first step in the EDP. 
3. Give each student a copy of the Design a Building Worksheet (PDF).
4. Provide students with the following design constraints:
5. 1. Each group has a $20 budget that cannot be exceeded.
   2. Each group’s building must be at least 30 cm tall.
   3. Each group’s building must sit within a 30-cm by 30-cm square.
5. Have students write down, in their own words, what the problem is that they are trying to solve on their Design a Building Worksheet (PDF).
6. Explain to students that they are diving into the second step of the engineering design process: research. (Engineers research what products or solutions already exist, and/or what technologies might be adaptable to their product.) Either at the library or with computers/laptop/tablet, allow students to research what materials absorb sound the best. Have them take notes on their Design a Building Worksheet (PDF).
7. Give students time to brainstorm what materials they would like to try to build their building. Remind students that they have a budget of $20 and engineers often work with time, size, and constraints on how much they can spend. Their notes should be included on their Design a Building Worksheet (PDF). Remind them to think about the research they did about what materials absorb sound well.
8. After imagining different ideas, each group plans by selecting their most promising solution and which materials they want to use. They should sketch their agreed upon design in their Design a Building Worksheet (PDF). At the same time, they should decide what materials they would like to purchase, how much they are, and add the costs for a final cost. Remind students that imagining and selecting the most promising solution are the third and fourth step of the engineering design process. 
9. Once the budget is checked by a teacher, have one student from each group take the materials they need from the materials display.
10. Give students time to dive into the fifth step of the EDP and create their buildings with their chosen materials. Remind students to record their design on their Design a Building Worksheet (PDF).

Figure 1. Decibel meter measuring 90 decibels from a test sound.CopyrightCopyright 2021 Kayla Sutcliffe, University of Florida MRETFigure 2. Decibel meter measuring 58 decibels from the sound of a plane after a model is designed.CopyrightCopyright 2021 Kayla Sutcliffe, University of Florida MRET

11. When a group finishes their design, have them move into the sixth step of the EDP and set up their test to evaluate their design.
12. 1. The sound meter should be placed inside the building. The loud sound should be made 1 meter away from the model. (see Figures 1 and 2). Try to keep the sound consistent to protect the reliability of the results.
    2. Every time the students test their design, they must record the decibels measured on their worksheets.
12. Have students determine what worked and what didn’t in their design. Remind students that they should learn from their failures and encourage them to use new materials to alter their designs and record what materials they will want for their next design iteration on their worksheets.
13. Have the groups complete the seventh step of the EDP as they work to improve their first design by creating more designs based on the decibels measured (number of times the students alter their design is at the teacher’s discretion). Each time students improve their designs, they may come up to the material area, and receive an extra $2 to spend on their redesign.
14. Give each group one piece of poster paper and markers to present their design process. Students should include the following on their poster:

• • Problem: Can we design a building that absorbs the loud sounds from a nearby airport? Can we do it without going over budget?
  • Drawing of their final design.
  • How many decibels were measured for each design/redesign? (A table might be very helpful here.)
  • What they changed in each design phase.
  • What they learned about absorption of certain materials.
  • How much money they spent and why budgeting matters in engineering.

Two students design a building to protect it from the sound of a plane.CopyrightCopyright 2021 Kayla Sutcliffe, University of Florida MRET

Pre-Activity Assessment

Quick Poll: Before the activity begins, ask students what materials they think will act as the best insulators for their buildings. If time allows, ask students to justify their answers.

Activity Embedded (Formative) Assessment

Worksheet: Students either work individually or with their group to complete the Design a Building Worksheet (PDF).

Post-Activity (Summative) Assessment

Presentation: Each group presents their devices and findings to the class as a poster or digital presentation. Teachers can use the Teacher Presentation Rubric (PDF) for assessment.

Discuss/think-pair-share: Ask students the following questions to encourage discussion:

• Which materials met our goal today of providing insulation and blocking sound? (Answers may vary based on students’ designs.)
• How did you act as materials engineers today? (Example answer: we used materials to solve a problem, designed something for someone to use, etc.)

Students might need to be reminded that loud sounds should not be made right next the ear.

• Test the sound meter you are using before using it for students to make sure it works.
• When students record data on their worksheets, some might need more help than others, depending on learning level. Encourage students to help each other record. Pictures are also acceptable forms of recording.