Lesson Decibels and Acoustical Engineering

Learning Objectives

After this lesson, students should be able to:

• Demonstrate and explain what type of materials absorb sound.
• Communicate the results of their research with their classmates.

Educational Standards

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.

NGSS: Next Generation Science Standards - Science

International Technology and Engineering Educators Association - Technology

State Standards

Worksheets and Attachments

Pre-Req Knowledge

Students need to have experience with adding and subtracting decimals to the hundredths place. Students should have experience with bar graphs or be able to identify a bar graph.

Introduction/Motivation

(Have students complete the Decibels Pre-Quiz to assess what they already know or have learned about sound energy.)

In this lesson, we will learn that sound is energy and has the ability to do work. So, what exactly is sound? Sound is produced by a vibration, and a vibration is when objects or air molecules rapidly move back and forth. When a vibration occurs, it produces sound. When the vibration stops, the sound produced stops as well. Sound travels in waves from one place to another. You can visualize this by imagining a person dropping a rock in a pond. The impact of the rock upon the surface of the water produces a ripple effect. Sound waves “ripple” from a vibration in a similar way. Sound waves need a medium or material to travel through and this material can be a solid, liquid, or gas. When a sound hits a material, it is either absorbed, reflected, transmitted, or a combination of all three. When a sound is absorbed, the waves are essentially disrupted by the material, making the sound dissipate. When a sound is reflected, it bounces off of the material and comes back to the person or object making the sound. When a sound is transmitted, the sound travels through the object.

(Use the first 10 slides of the Soundproof Challenge PowerPoint Presentation to build background knowledge. Lead the class into a discussion using the PowerPoint with the linked (and vetted) videos to learn and engage the students more about sound.)

Lesson Background and Concepts for Teachers

Distribute the Decibels Pre-Quiz to the class and assign the class to complete as much as they can of the pre-quiz. After the students are finished completing the pre-quiz, lead the class into an engaging discussion about sound energy referring to the Soundproof Challenge PowerPoint Presentation to give the students the necessary background knowledge for the two associated activities. The presentation covers a range of topics, including:

• What is Sound? (slide 2)
• How do we visually represent sound? (slide 3)
• How sound is created by vibrations. (slide 4)
• Sound travels in waves. (slide 5)
• Sound needs a medium through which to travel. (slide 6)
• Sound can be absorbed and reflected. (slides 7-8)
• An explanation of decibels. (slide 9)

Acoustical Engineers

Another key concept to consider (one that will serve to involve students further in the associated activities, What Soundproofing Material Works Best? and Design a Soundproof Room) is how we build structures in order to manipulate sound. Acoustical engineering is a field dedicated to understanding the science of sound and vibration. Engineers in this field, usually called acoustical engineers, apply acoustic in technology and typically work on projects design to analyze and control sound.

Acoustic engineers may work in a range of fields that help amplify sound or make sound more clearer, such as designing a symphonic hall or improving ultrasound devices. However, they may also deal with sound reduction or noise control, particularly for human and animal benefit. There are a range of sub-discplines associated with acoustical engineering. Examples include: aeroacoustics, or how sound moves through the air; electroacoustics, a discipline concerned with the design of sound amplification through technology; and ultrasonics, which deals with how sound waves move through solids, liquids, and gases at high frequencies.

Acoustical engineers should not be confused with audio engineers (or sound or recording engineers), even though sometimes the two designations overlap. Audio engineers work in a specific field designed to produce a live performance using a range of technology such as microphones, speakers, and amplifiers.

Before doing this lesson, ask the students to bring in boxes about two weeks prior. Tennis shoe or tissue boxes will work fine, and the boxes should be generally the same size.

• To prepare for the associated activities, the teacher will need to download the following apps on their smart phone:  Tone Generator (found at the App Store for free) and Decibel meter: Decibel X: dB, dBA Noise Meter (also found at the App store for free).
• The teacher should also assign the students into six separate groups.

Associated Activities

• What Soundproofing Material Works Best? - Students participate in an activity to help them learn about materials that absorb and reflect or transmit sounds.

  Watch this activity on YouTube

• Design a Soundproof Room - Students create a soundproof room in a follow-up activity using a shoebox “room” and various materials that are provided to them in class. The materials should be used to absorb the sound in the room so there is a reduction of sound coming from the room.

Vocabulary/Definitions

absorption: The process by which a material, structure, or object takes in sound energy when sound waves are encountered, as opposed to reflecting the energy.

acoustic: The branch of physics that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound, and infrasound.

decibel: A unit of measurement used to express the intensity of a sound, or the power level of an electrical signal by comparing it with a given level on a logarithmic scale.

medium: A material substance that can help move energy waves (such as sound) along. Also known as a transmission medium.

oscillation: The repetitive variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. The term vibration is precisely used to describe mechanical oscillation.

reflection: The change in direction of a wave at the fact of a medium so that the wave returns to where it originated.

sound: A vibration that manifests itself as a wave of pressure and can be perceived by humans (depending on the frequency) via the ear. Humans can hear soundwaves when the frequency lies between 20Hz and 20 kHz.

soundproof : The means of preventing sound by constructing material that prevents its passage and reflection.

transmit : In acoustics, sound passing from one area to another, normally through air or through a material constructed by some other medium.

vibration: In mechanics, an oscillation of the parts of a fluid or an elastic solid whose equilibrium has been disturbed, or of an electromagnetic wave.

wave: A wave of compression by which sound is propagated in an elastic medium such as air.

Assessment

Pre-Lesson Assessment

Pre-Quiz: Have students complete the Decibels Pre-Quiz to assess their knowledge on sound and reading a graph.

Homework

Homework: Students complete the Vocabulary Homework Sheet to practice using words relating to sound.

Additional Multimedia Support

Tone Generator: https://itunes.apple.com/us/app/tone-generator/id457003837?mt=8

Decibel X: dB, dBA Noise Meter: https://itunes.apple.com/us/app/decibel-x-db-dba-noise-meter/id448155923?mt=8

Copyright

Contributors

Supporting Program

Acknowledgements

This material is based upon work supported by the National Science Foundation under grant no. EEC 1405869—a collaborative Research Experience for Teachers Program titled, “Inspiring Next Generation High-Skilled Workforce in Advanced Manufacturing and Materials,” at the University of Dayton, Central State University and Wright State University in Ohio. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.