1. Calculate the speed of 25 cm ripples passing through water at 120 waves/s

2. Determine the l, f, & T of the 49th overtone of a 4
Determine the l, f, & T of the 49th overtone of a 4.0 m organ pipe when vsound = m/s

3. Chapter 15
Sound

4. Sound Waves
Longitudinal waves caused by pressure change producing compressions & rarefactions of particles in the medium

5. Sound Waves
Any vibrations produce regular oscillations pressure as the vibrating substance pushes air molecules back & forth

6. Sound Waves
The oscillating air molecule collide with others transmitting the pressure variations away from the source

7. Sound Waves
Air resistance will cause the amplitude of the wave to diminish as it moves away from the source

8. Speed of Sound
vsound in air = m/s
+ (0.60 m/soC)(T)

9. Speed of Sound
vsound ~ 343 m/s
At room temp.

10. Speed of Sound at 25oC
vin air = 343 m/s
vfresh water = 1493 m/s
vsea water = 1533 m/s
vin steel = 5130 m/s

11. The human ear can detect sound between 20 Hz & 16 kHz
The human ear can detect sound between 20 Hz & 16 kHz. Calculate the wavelength of each:

12. Calculate the l in mm of notes with frequencies of:
2.0 kHz & 10.0 kHz
vsound = 342 m/s

13. How loud sound is, is proportional to the amplitude of its waves
Loudness
How loud sound is, is proportional to the amplitude of its waves

14. Unit for measuring the loudness of a sound wave
Decibels (dB)
Unit for measuring the loudness of a sound wave

15. Decibels
Measured in log units
50 dB is 10 x greater than 40 dB

16. Pitch
Pitch is proportional to the frequency or inversely proportioned to the wavelength

17. Doppler Effect
Changes in observed pitch due to relative motion between the source & the observer of the sound wave

18. Doppler Effect
The pitch of approaching objects has higher frequencies or shorter wavelengths

19. Doppler Effect
The pitch of objects moving apart has lower frequencies or longer wavelengths

20. The Physics of Music

21. Almost all musical instruments are some form of an open tube or strings attached at two ends

22. In brass instruments, the lip vibrates against the mouthpiece causing the instrument to vibrate

23. In reed instruments, air moving over the reed causes it to vibrate causing the instrument to vibrate

24. In pipe instruments, air moving over the opening causes air to vibrate causing the instrument to vibrate

25. In stringed instruments, plucking the string causes it to vibrate causing the instrument to vibrate

26. In musical instruments, the sound is dependent upon resonance in air columns

27. In each instrument, the longest wavelength produced is twice the length of string or air column

28. When multiple objects vibrate at the same frequency or wavelength
Resonance
When multiple objects vibrate at the same frequency or wavelength

29. Resonance
Resonance increases amplitude or loudness as multiple sources reinforce the waves

30. Resonance
The length & width of the air column determine the pitch (frequency or wavelength)

31. Resonance
In instruments sound resonates at a fundamental pitch and many overtones

32. Calculate the wavelengths for each of the following sound frequencies at 30.83oC: 4.0 MHz & 10.0 MHz

33. The lowest tone or frequency that can be generated by an instrument
Fundamental
The lowest tone or frequency that can be generated by an instrument

34. Sound waves of higher frequency or pitch than the fundamental
Overtones
Sound waves of higher frequency or pitch than the fundamental

35. Pipe Resonance Open Pipe: open at both ends
Closed Pipe: Closed at one end

36. Pipe: Open End
High Pressure-antinode
Zero Displacement-node

37. Displacement antinode
Pipe: Closed End
Pressure node
Displacement antinode

38. A pipe that is closed at one end
Closed Pipe Resonator
A pipe that is closed at one end

39. A pipe that is open at both ends
Open Pipe Resonator
A pipe that is open at both ends

40. Wavelengths Generated by a Closed Pipe Resonator
= 4L/(2n +1)
f = v(2n+1)/4L

41. Wavelengths Generated by a Closed Pipe Resonator
n = 0 for the fundamental

42. n = positive integers for overtones
Wavelengths Generated by a Closed Pipe Resonator
n = positive integers for overtones

43. Typical Wavelengths Generated by CP

44. Wavelengths Generated by an Open Pipe Resonator
= 2L/(n+1)
f = (n+1)v/2L

45. Wavelengths Generated by an Open Pipe Resonator
n = 0 for the fundamental

46. n = positive integers for overtones
Wavelengths Generated by an Open Pipe Resonator
n = positive integers for overtones

47. Typical Wavelengths Generated by OP

48. Calculate the longest wavelength & the first two overtones produced using a 68.6 cm saxophone. (open)

49. Calculate the wavelengths & frequencies of the longest & the first 4 overtones produced using a 2.0 m tuba.

50. Calculate the wavelengths & frequencies of the lowest & the first 4 overtones produced using a 5.0 cm whistle. (closed)

51. Sound Quality

52. The lowest tone or frequency that can be generated by an instrument
Fundamental
The lowest tone or frequency that can be generated by an instrument

53. Sound waves of a higher frequency or pitch than the fundamental
Overtones
Sound waves of a higher frequency or pitch than the fundamental

54. Harmonics
Sound waves of higher frequency or pitch than the fundamental or overtones

55. Addition of all harmonics generated determines timbre
Quality of sound
Addition of all harmonics generated determines timbre

56. Beat Oscillations in sound wave amplitude
Can be produced by wave reinforcement

57. Consonance
Several pitches produced simultaneously producing a pleasant sound called a: Chord

58. Dissonance
Several pitches produced simultaneously producing an unpleasant sound or:
Dischord

59. Consonance
Consonance occurs when the frequencies having small whole number ratios

60. Consonance Frequency Ratios
2:3
3:4
4:5

61. Consonance Frequency Ratios
The notes in the chord C major have frequency ratios of 4:5:6

62. Octave
When two notes with a frequency ratio of 2:1, the higher note is one octave above the lower note

63. Frequency Ratios 1:2 - octave 2:3 - Perfect Fifth 3:4 - Perfect Fourth
4:5 - Major Third

64. A mixture of a large number of unrelated frequencies
Noise
A mixture of a large number of unrelated frequencies

65. Determine the l, f, & T of the 19th overtone of a 50
Determine the l, f, & T of the 19th overtone of a 50.0 cm open tube when vsound = m/s

66. Determine the l, f, & T of the 9th & 14th overtone of a 80
Determine the l, f, & T of the 9th & 14th overtone of a 80.0 cm open tube when vsound = m/s

67. Determine the l, f, & T of the fundamental & 1st three overtones of a mm open tube when vsound = m/s