Feel The Noise


Author:

David Macmorine

Unit Title:

Feel The Noise

Grade:

11-12

Subject:

Pre-Calculus

Estimated Duration:

2 Weeks

Unit Activities:

Activity 1: What is sound?

Activity 2: Understanding Sound Measurement

Activity 3: Understanding Sound Measurement

Background Knowledge: 

Knowledge of logarithms is needed to calculate in the decibel scale.

Date:

July 2014

The Big Idea (including global relevance)

Noise pollution is a growing problem with our crowded, urbanized society.  Population density, coupled with noise generated by transportation, mechanization, entertainment, etc. leads to more noise and the problems that come with noise.  Studies have shown excessive noise may lead to health issues such as increased blood pressure, heart disease, and lack of sleep. 

Video on how sound travels in a room –

https://www.youtube.com/watch?v=JPYt10zrclQ

Videos on noise and health -

https://www.youtube.com/watch?v=6y7BkkW42v8

https://www.youtube.com/watch?v=QZSHpmWu54I

https://www.youtube.com/watch?v=-coWNwt5qHQ

Videos on sound absorption –

https://www.youtube.com/watch?v=N1KaCfjrMzM

https://www.youtube.com/watch?v=wxRtiGexwPM

https://www.youtube.com/watch?v=ayQXA_hd6yk

The Essential Question

How can we reduce sound pollution?

Justification for Selection of Content

Sound reduction and abatement are topics of acoustic engineering.  Architects must design modern structures to account for noise reduction and abatement.  The mathematics of decibels which are based upon a logarithmic scale are necessary, as well as the Inverse Square Law for the study of non-linear mathematics.  Logarithms are a subject students frequently struggle with.

The Challenge

Students will design a box to reduce the level of a sound from a frequency of 2000 hz at an acceptable level (i.e. 60 dB) on the outside to reduce the inside decibel level by 20 dB.   The frequency will then be reduced to 1000 hz  and then the challenge repeated.  

The Hook

Have you ever been bothered by noise?

Teacher's Guiding Questions
  • Have you ever been annoyed by sound?
  • Have you ever lost sleep because it was too noisy?
  • Is noise a health issue?
  • What is hearing damage?
  • Have you ever seen a large highway wall?  Why is it there?
  • What is an echo?

  • Is there a difference between noise and sound?
  • Does everyone have the same ability to hear?
  • Can you hear sounds that I can’t?
  • What is hearing damage?
  • How does sound travel?
  • How is sound measured?
ACS (Real world applications; career connections; societal impact)

Applications:  Real world applications include noise abatement and elimination for highway, airport and building construction. 

Career Connections; Civil engineering and architecture, and sound recording and control for sound engineers.

Societal Impact:  Noise elimination and control is necessary for quality of life and improved physical and mental health in our increasingly crowded society. 

Engineering Design Process (EDP)

Students will design a box consisting of sound deadening and/or eliminating material. Sound will be generated outside of the box at an acceptable decibel level (such as 60 dB) and a frequency of 2000 hz.  A decibel meter will be placed in the box with a camera connected to a computer to record the sound level in the box. The sound level must be reduced by 20 dB.  The frequency will then be decreased to 1000  hz and the challenge repeated. 

Unit Academic Standard

1-PS4-1. Plan and conduct investigations to provide evidence that vibrating materials can make sound and that sound can make materials vibrate.

1-PS4-4. Use tools and materials to design and build a device that uses light or sound to solve the problem of communicating over a distance. 

Unit Activities
  • Lesson on the nature of sound and sound measurement in decibels
    • Activity on the speed of sound
    • Activity on the definition of the decibel scale
  • Lesson on measuring sound with a sound meter
    • Activity on reading and understanding a decibel meter
    • Activity on sound pollution and the Inverse Square Law
  • Lesson on soundproofing
    • Activity on designing a soundproof box
    • Activity on testing the effectiveness of the box
    • Redesign of for a different frequency
Where the CBL and EDP appear in the Unit

Activities 3 worksheet e and f

Misconceptions

Sound is measured from an arbitrary level of 10^-12 watts per square meter. This is a very small quantity which necessitates the use of a logarithmic scale.

Pre-Unit Assessment Instrument
Post-Unit Assessment Instrument
Results: Evidence of Growth in Student Learning
After teaching the Unit, present the evidence below that growth in learning was measured through one of the instruments identified above.  Show results of assessment data that prove growth in learning occurred.
How to Make This a Hierarchical Unit

The Unit could be used in the middle school classroom by presenting logarithms as a ‘math tool’ to help with small numbers.  Worksheet b could be approached this way, and worksheet d could be ignored due to inverse square mathematics.  The use of decibels as simply a measuring tool could be emphasized. 

Reflection

The Unit was quite successful and worked much better than I thought it would.  I believe the ‘hook’ of examining noise, being unwanted sound, was a common problem for all of my students.  The videos linked in the lesson went over very well, especially the video from Acoustic Geometry.  The videos provided interest and motivation in the material. 

One of the difficulties arose during the measure of sound in the decibel level.  I had a very good decibel meter and my students were using cell phone apps to measure decibel levels.  Both measuring tools would not give the same measurement from the same sound source.  It was determined the microphone used by cell phones is not as sensitive to sound as a professional model.  Therefore to measure for the challenge, generate a sound at a reasonable decibel level and measure it.  Then measure the level inside the device to achieve the 20 dB reduction. 

Materials used to build the devices were both accessible and inexpensive.  The most expensive material is the Dynomat, or as I used, a roof re-enforcement patching tape.  It comes in a roll from the hardware store and is an aluminum backed rubberized tape.

It was also necessary to have a cable to go from the ¼ inch standard amplifier jack to the 1/8th inch headphone jack of a cell phone.