A segment of our curriculum documents for physics - on the unit I am currently teaching, sound, looks as follows: (taken from the physics curriculum)
Unit 13: Sound and Music (1 week)
A. Instructional Goals and Objectives
Instruction Goal #1: To show that sound is longitudinal and mechanical wave motion.
Objective #1: To find the speed of sound in air.
Objective #2: To see that echo is important property of sound.
Objective #3: To find that reverberation is a property of brains, not sounds.
Instructional Goal #2: To demonstrate the quality of sound as it pertains to music
Objective #1: To learn about timbre.
Objective #2: To demonstrate resonance.
Objective #3: To see beats and interference in action.
Instructional Goal #3: To learn about the properties of sound that are important to biological creatures and the physical environment.
Objective #1: To learn about loudness in terms of decibels.
Objective #2: To see how creatures can use the Doppler Effect to locate and describe objects using sound waves.
Objective #3: To identify that the speed of sound is determined by the composition of a material.
B. Unit Overview
Introductory Demonstration: Bell in a Jar
Lab#1: Title: Speed of Sound
Activity #1 Title: Tuning fork spun in a circle
Worksheet: Title: Speed of Sound
Quiz 1: Title Sound Basics
Lab #2: Title: Doppler Effect
Worksheet #2: Title: Bats and Dolphins
Quiz 2: Title: Doppler Effect
Test: Sound
C. The Learning Cycle
Elicit
Find a tuning fork set and make beats with them. Do you know what is happening?
Engagement
How can one tuning fork affect another?
What is the speed of sound in air?
What is the speed of sound in water?
How loud is an airplane from 10m, 100m, 1000m away.
What is the concept of Intensity of sound?
How can the speed of sound be found in class?
Do the Echo/Reverb demonstration outside.
Spin the tuning fork in a circle
Play the sounds of police sirens coming at us and away from us.
Exploration
Hands On Activity/Laboratory Title: PVC pipe and tuning fork
Pre-Lab Discussion: How can this apparatus be used to find the speed of sound?
The lengthening of the air column will elicit amplitude matching and therefore a relationship in the length of column and frequency of pitchfork can be established
The relationship can be used to develop a graph of f v wavelength.
The students may not realize that it is only ¼ of the wavelength, but the relationship exists nonetheless.
Additional information
Draw a picture on the board of 2 dimensional wave inside pipe.
Students marking the pipe with pencil and measuring separately will get the best results.
Explanation
Characteristics of Sound. As beings that hear, we should be thankful for three things that make it all possible; sound waves, air (as a medium), and our ears to receive the sound waves. Sound CANNOT travel in the absence of matter. Without a medium, we wouldn’t be able to hear a thing.
Speed of Sound – related to both the elasticity of the medium and the density of the medium.
v = √(B/ρ)
where B is the elastic modulus and ρ is density.
In air, as the density increases, the velocity decreases. The speed of sound at 20 degrees Celsius is 343 m/s where as at 0 degrees Celsius it is 331 m/s.
Other speed of sound examples at 20 degrees Celsius and 1 atmosphere include:
Water 1440m/s
Seawater 1560m/s
Glass 4500m/s
Aluminum 5100m/s
Although sound slows down in colder air, if we move to a denser medium and much more elastic medium, (such as a liquid or solid), the speed of sound increases a lot.
Sound travels fastest through very elastic solids.
IQ question: If the speed of light is 3 x 108 m/s and the speed of sound is 340 m/s, then how can we tell how far away a thunderstorm is based on this information?
There are two aspects of sound; loudness (related to amplitude) and pitch (related to frequency).
Loudness – related to the energy in the sound wave.
Pitch – sound refers to whether it is high, like the sound of a violin, or low, like the sound of a base drum. The pitch is the frequency of the sound.
Audible Range – the range of frequencies that the human ear can hear (20Hz – 20,000Hz).
Ultrasonic – frequencies above 20,000 Hz.
Example: dog whistle
Infrasonic – frequencies below 20 Hz.
Example: earthquakes, volcanoes
Pressure waves – another name for longitudinal waves due the compressions (high pressure) and rarefaction (low pressure).
Intensity of Sound: Decibels
Intensity (I) – a physically measurable quantity of the energy transported by a wave per unit time across unit area. (it is proportional to the square of the amplitude of the wave). The units are Watts/meter2 or (W/m2)
Our intensity range is 10-12 W/m2 to 1 W/m2 (very painful and damaging to hear)
The loudness increases proportionally to the intensity. If the sound is increased by a magnitude of 10 W/m2, then it sounds twice as loud to our human ear.
Decibel (dB) – scale name after Alexander Graham Bell, used to describe the loudness in terms of intensity.
Intensity level (β in dB) is defined as
β(in dB) = 10 log (I/Io)
where I and Io represent the final intensity and initial intensity, respectively.
Amplitude Related to Intensity
A = 1/πf (I/2ρv)
Below is a list from the Noise Center of decibels we are exposed to:
Home
50 refrigerator
50 - 60 electric toothbrush
50 - 75 washing machine
50 - 75 air conditioner
50 - 80 electric shaver
55 coffee percolator
55 - 70 dishwasher
60 sewing machine
60 - 85 vacuum cleaner
60 - 95 hair dryer
65 - 80 alarm clock
70 TV audio
70 - 80 coffee grinder
70 - 95 garbage disposal
75 - 85 flush toilet
80 pop-up toaster
80 doorbell
80 ringing telephone
80 whistling kettle
80 - 90 food mixer or processor
80 - 90 blender
80 - 95 garbage disposal
110 baby crying
110 squeaky toy held close to the ear
135 noisy squeeze toys
Work
40 quiet office, library
50 large office
65 - 95 power lawn mower
80 manual machine, tools
85 handsaw
90 tractor
90 - 115 subway
95 electric drill
100 factory machinery
100 woodworking class
105 snow blower
110 power saw
110 leafblower
120 chain saw, hammer on nail
120 pneumatic drills, heavy machine
120 jet plane (at ramp)
120 ambulance siren
125 chain saw
130 jackhammer, power drill
130 air raid
130 percussion section at symphony
140 airplane taking off
150 jet engine taking off
150 artillery fire at 500 feet
180 rocket launching from pad
Recreation
40 quiet residential area
70 freeway traffic
85 heavy traffic, noisy restaurant
90 truck, shouted conversation
95 - 110 motorcycle
100 snowmobile
100 school dance, boom box
110 disco
110 busy video arcade
110 symphony concert
110 car horn
110 -120 rock concert
112 personal cassette player on high
117 football game (stadium)
120 band concert
125 auto stereo (factory installed)
130 stock car races
143 bicycle horn
150 firecracker
156 capgun
157 balloon pop
162 fireworks (at 3 feet)
163 rifle
166 handgun
170 shotgun
Sound
Sources of Sound: Vibrating Strings and Air Columns
In music we make sound by striking, plucking, bowing, or blowing. Standing waves are produced which cause the air (or medium) to vibrate and the sound waves reach our ear and we hear the music.
When we talk about music, each octave is simply doubling the frequency.
Pitch directly relates to frequency. The musical scale is generally called an “equally tempered chromatic scale.”
Fundamental Frequency – the lowest resonant frequency.
Remember that v = λf. As we decrease the wavelength, the frequency gets higher.
If we place a node directly in the middle of the fundamental frequency, then we get a harmonic or overtone. These are higher-frequency standing waves.
· Sound
Quality of Sound, and Noise When we hear a sound, we are aware of its pitch, loudness, and quality. We’d say some sounds are better quality than others. You can never mistake a guitar for a piano even if you play a note at the same loudness and pitch.
Quality (or timbre): tone distinctive to a particular voice, instrument, or sound.
The quality depends on the amount of overtones
the number of overtones
their relative amplitudes
You can affect the tone quality also by the way you play the instrument. For example, if you pluck the violin or use a bowstring, you get very different sound because of how long the note lasts or is held.
Noise – sounds of many frequencies together that have no comparisons to one another.
When a sound is a quality sound, the overtones relate to the fundamental tone. With noise, none of the frequencies relate.
Noise can relate to psychological problems or annoyance of the mind. We can also lose hearing if we hear too much noise.
Although noise hurts our hearing, it is very difficult to control. Ear protection is our best defense against it.
Interference of Sound Waves; Beats
When two waves pass through the same region at the same time, they interfere with one another. If you stand in one spot and two speakers are facing you, there’s a chance that you may hear them or not hear them at all depending on where you are standing. If the waves meet in phase with one another where you are, then you will hear a loud sound due to constructive interference. If you are standing where the waves from each speaker are out of phase, you will hardly hear anything because you’re standing in a deconstructive area.
Beats – the phenomenon that occurs if two sources of sound – say, two tuning forks – are close in frequency but not exactly the same. Sound waves from the two sources interfere with each other and the sound level at a given position alternately rises and falls; the regularly spaced intensity changes are called beats.
Beat Frequency – the difference in frequency of the two waves. (time it and invert the time).
Sound
· Doppler Effect
Doppler Effect – When a source sound is moving towards an observer, the pitch is higher than when the source is at rest; and when the source is traveling away from the observer, the pitch is lower.
Perform ball demo here to show how the pitch changes. The pitch increases as it is approaching an observer because the source is catching up to the sound wave traveling away from it. Since it is catching up, it decreases the wavelength between the waves, and therefore increases the pitch. On the other hand, when a the source is moving away from the observer, the source is pulling away from the sound wave as the sound wave travels towards the observer. This increases the distance between each wave and therefore lowers the frequency. To calculate the new frequency, we need the speed of the observer, the source of the sound, and the frequency of the source when it is not in motion.
f’ = f ((v +- vobs)/(v+-vsource))
· Shock Wave and the Sonic Boom
Supersonic speed – faster than the speed of sound
Mach number – ratio of the object’s speed to that of sound in the medium at that location. For example – a plane traveling 680 m/s in air where sound travels 340 m/s has a speed of Mach 2.
Shock Wave – when a source of sound moves faster than the speed of sound.
Sonic boom – the phenomenon that occurs when the speed of sound is broken. All of the compressions of the sound waves being produced are on top of each other since the plane or object is moving with the sound waves at the speed of sound. When all of the compressions are on top of one another, it creates a boom due to the constructive interference.
· Applications; Ultrasound and Medical Imaging
Sonar (sound navigation and ranging) – pulse –echo technique is used to locate underwater objects. A sound pulse is sent through the water and a detector receives its reflection or echo a short time later. This is timed and based on the speed of sound, a distance is calculated.
Ultrasonic – used in medicine to destroy unwanted tissue in the body, to create an image of internal organs, for pregnancy images.
A pulse-echo technique – like sonar, it’s used as an imaging technique to see into the body. It’s a way to see if there are growths on organs or pockets of fluid in the body.
Elaboration
Some of the items listed above can be used to explain what they have learned in the labs.
Application of new knowledge to how bats and dolphins find food is key to earlier biological lessons.
The chemical bond makeup becomes paramount to understanding how the sound moves through materials.
Defining mathematical relationships and graphing will link strongly to prior trigonometry skills, and equation building is really the first venture towards becoming an aware physicist.
Evaluation
Ongoing assessments of students will be made, including discussions, homework assignments, lab reports, quizzes, lab notebook checks, chapter tests and unit tests to continuously evaluate the comprehension and development of all students.
Additional Information
Formative evaluation of students is an ongoing process, not limited to one phase of the learning cycle.
Tests should provide students with opportunities from the lab experience, including interpreting data tables, performing lab-based calculations, designing lab experiments, etc.
Extend
Is light capable of moving in a medium?
Have students tune up wine glasses with water, and play a song like Twinkle, Twinkle Little Star.
D. Required Resources
· PVC pipes
· Water containers
· Tuning forks
· Beat Box Tuning Forks
· Sound microphone
· Glasses
· Vacuum Jar
· Balloons
· Rulers
· Computers with microphones
E. Suggested Additional Activities & Resources (including technology integration, if applicable)
· Have students tune up wine glasses with water, and play a song like Twinkle, Twinkle Little Star using Logger Pro and microphones.
Our curriculum documents for physics given here are more traditional in their format and are divided into six categories which are -
- Instructional goals and objectives.
- Unit Overview which includes suggested demos, labs, activities, and assessments.
- The Learning Cycle - an explanation of the specifics of the unit that covers engagement, exploration, explanation, elaboration, and evaluation.
- Extend - application of material - critical thinking skills.
- Required resources such as technology integration.
- Suggested additional activities and resources.
As an additional point, I tend to use my own version which is based on the UbD curriculum model. I incorporate both essential questions and enduring understandings at the beginning of each unit. This guides the assessments I develop and then in turns leads me to my activities.
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