Introduction to Sound Waves
8th grade Science
The lesson will introduce students to sound as a waveform. Students will be shown demonstrations of hand-made musical instruments. Students will learn that wavelength and frequency are related and that pitch is related to frequency. Students will be able to visualize sound wave propagation and contrast it to light wave propagation. Students will be able to explain echoes, pitch, and the doppler effect
Is sound comprised of waves?
How is frequency related to pitch?
How does sound travel from one place to another?
What is the Doppler effect and what is a sonic boom?
Students should be able to identify the two (three) main components of a wave: amplitude and frequency (wavelength). Students should be able to compare and contrast light and sound waves. Students should understand that a higher frequency of sound leads to a higher pitch. Students should be able to visually describe the doppler effect and sonic boom.
Laptop, projectors, PowerPoint, student lab notebooks.
4 Mason jars or coke cans with different amounts of water inside
Either a homemade wind instrument or a board with thumbtacks with rubber bands of differing tension
“Standing Waves Part I: Demonstration” – https://www.youtube.com/watch?v=-gr7KmTOrx0
“Really Cool Doppler effect video” – https://www.youtube.com/watch?v=Djz_rtnXSfY
Sound: Vibrations that travel through air
Pitch: How high a sound is to our ears
Amplitude: How big a wave is
Doppler Effect: An object moves while it emits sound: in front it sounds high pitched but in back it sounds low pitched
Sonic Boom: An object moves faster than the speed of sound
Students will have learned about light waves and the concept of wavelength/frequency. Students will understand that light has a constant speed.
1.) Do Now: Copy vocabulary and definitions in student notebook
2.) Students will be shown 2 different types of handmade musical instruments. In a quick write, students will be asked to predict which mason jar and which rubber band will elicit the highest/lowest pitch sound. After the demonstration, the YouTube video “Standing Waves Part I: Demonstration” will be shown.
3.) Students will be given a mini notes sheet with lines for notes on the top half and a box for drawing on the bottom half.
4.) Students will be given notes about sound waves:
- Waves have wavelength and frequency
- Wide waves have high wavelength and low frequency (how fast it traveled down the rope)
- Skinny waves have low wavelength and high frequency (how fast it traveled down the rope)
- Sound is a wave
- Sound waves start as vibrations that move as a wave through air
- The faster the waves are, the higher pitched they sound to us
- The bigger the musical instrument, the higher the wavelength and the lower the frequency. That’s why the double bass sounds so low and the violin sounds high
4.) Students will be shown videos of police sirens, tornado sirens, and fighter jets and be prompted with a quick write: “What do these sounds all have in common”. Students will then be shown the YouTube video “Really Cool Doppler effect video” which demonstrates the pitch of the emitted sound from the perspective of the observer and moving source.
5.) Students will be shown a picture of a fighter jet with lines of sound drawn around the jet when it is not moving and when it is moving. Students will be asked to copy the images and determine if pitch is high or low for the moving jet at point A (in front of the jet) and point B (behind the jet).
Optional Engagement Enginering Activity
Students will be provided corkboard, thumbtacks, and rubber bands and are challenged to make a rubber band guitar that can play the “Ode to Joy” tune and will be judged on their accuracy by their classmates.
This lesson will conclude my teaching experience at Everett and will be one of the last lessons the students will have in 8th grade. Logically, the next lesson could discuss the propagation of sound waves in different mediums and students would be able to learn the basics of refraction of light and sound in different mediums.