1. Sound Waves

2. What are some (essential) questions?

3. Essential Questions: What are the facts and measurements to know?
What kind of wave is a sound wave?
Which measurement affects if a sound is high or low?
Which measurement affects if a sound is loud or quiet?
Which wave phenomena do sound waves demonstrate? Which are most important?
Skim PCR Sound Lessons 1-3

4. Essential Questions: On PhET, play with Wave Interference, Sound Tab
What does changing the frequency do to other wave measurements?
What does changing the amplitude do to other wave measurements?
Select two speakers. What do you observe? Repeat #1,2 w/ two speakers.
Select one slit, then two. Adjust width. What do you notice?

5. Facts and Measurements
Sound is a longitudinal mechanical wave with:
compression: region where the medium is “squeezed” together
rarefaction: region where the medium is pulled apart
Wavelength: distance from one compression to the next
Pressure Amplitude: difference between the relaxed pressure in the medium and the max or min pressure

6. What does it sound like?
The perception of the frequency is the PITCH (simple!)
The perception of the (pressure) amplitude is the INTENSITY LEVEL (complicated!)
b = (10dB) log (I/Io)
I = P/A

7. Which Wave Phenomena… ALL! Reflection (echo)
Interference (beats, resonance)
Doppler effect (Chipmunks to Barry White)
Refraction (yelling across a pond…)
Diffraction (yelling through a megaphone)

8. Lesson 4&5: Resonance Natural Frequency Forced Vibrations
Standing Wave Patterns
Resonance
Strings
Open End Air Columns
Closed End Air Columns

9. Resonance in Closed End Air Column (pipe)

10. Generate the lowest frequency “standing wave” pattern in a closed end pipe, then take appropriate measurements and perform appropriate computations to determine the speed of sound in the air. Repeat for two other frequency sounds.
State the objective
Draw the wave pattern, labelling the fractional wavelength and the length of the pipe (distance between ends)
Present measurements and computed values in a table
Show formulas, and “sample” calculations (with measurements plugged in) for one of the frequencies.
Average result and state in a concluding sentence.

11. Procedure:
Using an approximate speed of 340 m/s, compute the pipe length needed for fundamental frequency
Get a pipe that is a little longer
Make resonance happen, measure pipe length.
Compute experimental speed of sound.