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

2. Determine the, f, & T of the 49 th overtone of a 4.0 m organ pipe when v sound = 350.0 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 v sound in air = 331.5 m/s + (0.60 m/s o C)(T)

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

10. Speed of Sound at 25 o C v in air = 343 m/s v fresh water = 1493 m/s v sea water = 1533 m/s v in steel = 5130 m/s

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

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

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

14. 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. 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 30.83 o C: 4.0 MHz & 10.0 MHz

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

34. 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. Pipe: Closed End Pressure node Displacement antinode

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

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

43. Typical Wavelengths Generated by CP 0 = 4L 1 = 4L/3 2 = 4L/5

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

47. Typical Wavelengths Generated by OP 0 = 2L 1 = 2L/2 2 = 2L/3

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

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

65. Determine the, f, & T of the 19 th overtone of a 50.0 cm open tube when v sound = 350.0 m/s

66. Determine the, f, & T of the 9 th & 14 th overtone of a 80.0 cm open tube when v sound = 350.0 m/s

67. Determine the, f, & T of the fundamental & 1 st three overtones of a 700.0 mm open tube when v sound = 350.0 m/s