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. How can we write a general equation
That takes into consideration: ¼, ¾,5/4 …
That is similar to the equation we used for waves on a rope?
L = n/2 wavelengths

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

6. Investigation C here

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

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

9. 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. What is velocity of the wave in the tube? (do not forget the correction factor!!!)

10. More fun questions
A) If the temperature of a room filled with air is 32OC (at one atmosphere of pressure), what is the velocity of a sound wave in the room?
The answer: m/s
331 m/s + (.6 x every 1O above OO C)

11. Doppler effect here

12. Acoustics