The Physics Classroom » Concept Builders » Waves and Sound » Decibel Scale » Teacher Notes

Notes:

The Decibel Scale Concept Builder is an adjustable-size file that displays nicely on smart phones, on tablets such as the iPad, on Chromebooks, and on laptops and desktops. The size of the Concept Builder can be scaled to fit the device that it is displayed on. The compatibility with smart phones, iPads, other tablets, and Chromebooks make it a perfect tool for use in a 1:1 classroom.

 

Teaching Ideas and Suggestions:

Most Physics courses that include the topic of sound will at least mention the concept of a deciBel. It is a term that most of our students have heard prior to taking the course; they have an inherent interest in learning about the term. But many high school teachers shy away from the concept because of the complexity of the mathematics. This Concept Builder gives deciBels some strong conceptual meaning and is easy enough for inclusion in a Conceptual-level course that de-emphasizes algebraic formulae and mathematics. 

There are 36 questions in the Concept Builder. The questions are organized into 12 Question Groups and spread across three difficulty levels. Each question looks rather similar. The deciBel rating of Sound Source A is stated. Sound Source B is said to be X times more intense that Sound Source A. Students must determine the deciBel rating of Sound Source B. The X of "X times more intense" is always some power of 10 - for instance, 10 times, 100 times, 1000 times, etc. Each question is accompanied by a diagram of a deciBel scale with markings every 10 dB apart. The deciBel rating of Sound Source A is marked in red along the scale. Teachers can use the scale to help students understand the meaning of a deciBel rating.

The three difficulty levels differ in terms of the number of questions that must be answered and in the complexity of the ratios of intensities of the two sound sources. The three difficulty levels can be described as follows:
 
  • Apprentice: Question Groups 1-4. Includes only 4 Question Groups. The ratio between the intensities of the two sounds is at most three powers of ten.
  • Master: Question Groups 1-8. Includes the first four Question Groups plug four additional Question Groups. The ratio of the two sound intensities can be as high as six powers of ten.
  • Wizard: Question Groups 5-12. Includes the middle four Question Groups plus four additional Question Groups. The ratio of the two sound intensities can be as high as eight powers of ten.

There is a little redundancy from level to level. For instance, the Master Difficulty Level includes all the questions from the Apprentice Difficulty Level. And the Wizard Difficulty Level includes the four most difficult questions from the Master Difficulty level.
 
To gain a feel for the cognitive difficulty of this Concept Builder, we recommend that teachers attempt to complete one of the difficulty levels. Alternatively, the questions are provided in a separate file for preview purposes. In order to complete an activity, a student must correctly analyze each question for that difficulty level. If a student's analysis is incorrect, then the student will have to correctly analyze the same or very similar question twice in order to successfully complete the activity. This approach provides the student extra practice on questions for which they exhibited difficulty. As a student progresses through a difficulty level, a system of stars and other indicators are used to indicate progress on the level. A star is an indicator of correctly analyzing the question. Once a star is earned, that question is removed from the que of questions to be analyzed. Each situation is color-coded with either a yellow or a red box. A red box indicates that the student has incorrectly analyzed the question and will have to correctly analyze it twice before earning a star. A yellow box is an indicator that the question must be correctly analyzed one time in order to earn a star. Once every question for a difficulty level has been analyzed, the student earns a Trophy which is displayed on the Main Menu. This system of stars and Trophies allows a teacher to easily check-off student progress or offer credit for completing assigned activities.

The most valuable (and most overlooked) aspect of this Concept Builder is the Help Me! feature. Each question group is accompanied by a Help page that discusses the specifics of the question. This Help feature transforms the activity from a question-answering activity into a concept-building activity. The student who takes the time to use the Help pages can be transformed from a guesser to a learner and from an unsure student to a confident student. The "meat and potatoes" of the Help pages are in the sections titled "How to Think About This Situation:" Students need to be encouraged by teachers to use the Help Me! button and to read this section of the page. A student that takes time to reflect upon how they are answering the question and how an expert would think about the situation can transform their naivete into expertise. 

 

 

Related Resources

There are a few resources at The Physics Classroom website that serve as very complementary supports for the Decibel Scale Concept Builder. These include:
 
  • Minds On Physics Internet Modules:
    The Minds On Physics Internet Modules include a collection of interactive questioning modules that help learners assess their understanding of physics concepts and solidify those understandings by answering questions that require higher-order thinking. Assignments SM3 of the Sound and Music module provides a great complement to this Concept Builder. It is best used in the middle to later stages of the learning cycle. Visit the Minds On Physics Internet Modules.

    Users may find that the App version of Minds On Physics works best on their devices. The App Version can be found at the Minds On Physics the App section of our website. The Static Electricity module can be found on Part 5 of the six-part App series. Visit Minds On Physics the App.

     
 
 
 

Additional resources and ideas for incorporating this Decibel Scale Concept Builder into an instructional unit on Sound Waves can be found at the Teacher Toolkits section of The Physics Classroom website.  Visit Teacher Toolkits.