1. Sound Waves
And you

2. Sound waves
Longitudinal waves = particle motion in same direction as energy motion
Hearing ~ 20 to 20,000 Hz (sound generator)
Loudness = amplitude
Pitch = frequency
Rubens tube: tone generator and “the lion sleeps tonight”

3. Closed tube waves
1st mode = ¼ λ node at closed end anti node at open end
antinode
1st harmonic (overtone)
L = ¼ λ
2nd harmonic
L = ¾ λ
3rd harmonic
L = 5/4 λ

4. Odd series of #s math relationship
L = (2n – 1) / λ
λ = v/f
So the L = (2n – 1) / v/f

5. Investigation C here

6. Sound videos https://www.youtube.com/watch?v=Ude8pPjawKI

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

8. Follow up questions
A) A Rubens tube filled with propane gas has a measured λ of 1.81m when a tone of 246 Hz is used. What is the speed of the sound wave in the propane?
B) The first fundamental frequency is produced in a tube with a measured length of 0.32m and a diameter of 11cm using a 247 Hz tone. According to the method you used in your investigation, what is velocity of the wave in the tube? (do not forget the correction factor!!!)

9. The answers
A) 445 m/s
B) m/s

10. More fun questions
A) If the temperature of a room filled with air is 32OC (at one atmosphere of pressure), what is the “true” velocity of a sound wave in the room? (recall your investigation)
The answer: m/s

11. Diffraction
Apparent bending of waves around obstacles and spreading out of waves past an opening.

12. Wave interference
* Sound wave interference demonstration with tone generator
and students moving around in the room.

13. Doppler effect ppt. here