Sound Waves. and their characteristics. 1) Frequency (pitch) 2) Intensity (loudness) 3) Harmonic Content. May 10 11:45 AM

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1 Sound Waves and their characteristics 1) Frequency (pitch) 2) Intensity (loudness) 3) Harmonic Content May 10 11:45 AM 1

2 particle motion this one sound waves and the ear drum May 9 9:02 AM 2

3 sound waves and the ear drum May 7 6:52 AM 3

4 May 10 7:30 AM 4

5 May 10 7:30 AM 5

6 sound as a pressure wave May 7 6:56 AM 6

7 Sound the speed of sound vs = 331 m/s at 0 C +.6 m/s per C at 20 C the velocity of sound would be? 20 C (.6 m/s/ C) = 12 m/s therefore, at 20 C, 331 m/s + 12 m/s = 343 m/s May 9 10:16 AM 7

8 Sound is a longitudinal (compressional) wave the base wave equation is: vs = fλ characteristics: 1) Frequency (pitch) determined by source humans hear between 20 Hz 20,000 Hz lowest sound = 20 Hz v = fλ λ = v/f = 340 m/s/20 Hz = 17 m highest sound = 20,000 Hz v = fλ λ = v/f = 340 m/s/20,000 Hz = m lower vs higher frequency pitch May 9 10:18 AM 8

9 speech threshold of hearing What is the softest the sound can be to be heard. threshold of pain At what loudness do the sound cause pain. May 9 9:49 AM 9

10 Difference between a high frequency sound and a low frequency sound. May 9 12:07 PM 10

11 noise vs tone May 9 9:07 AM 11

12 Doppler Shift car horn still slower than vs vs faster than vs May 9 9:49 AM 12

13 Frequency you hear Velocity of sound listener velocity (detector) Source frequency Source velocity May 8 6:56 AM 13

14 multiplier May 13 10:21 AM 14

15 multiplier May 13 10:29 AM 15

16 bullet at mach 1.01, note shock wave just in front of the bullet May 10 9:33 AM 16

17 bullet at mach 2.45 May 10 9:35 AM 17

18 May 10 9:33 AM 18

19 2) Difference in amplitudes loudness May 9 12:08 PM 19

20 Difference in Intensities May 9 12:42 PM 20

21 Range of Intensities we hear softest W/m 2 threshold of hearing loudest 10 0 W/m 2 (1 W/m 2 ) threshold of pain range in intensities that's alot May 10 10:15 AM 21

22 Loudness ex: A sound is radiated from a source at 25 watts of power and is 10 m away. What is the intensity of the sound? I = P/ 4πr 2 = 25 W/ 4π(10m) 2 I =.02 W/m 2 Power = P = E/t = W/t = Fd/t, or Fv Area the sound wave covers per unit of time is the surface area of a sphere A = 4πr 2 May 9 10:46 AM 22

23 May 9 11:28 AM 23

24 May 18 7:28 AM 24

25 May 18 7:29 AM 25

26 May 10 10:18 AM 26

27 sound at threshold of pain May 10 8:09 AM 27

28 sound wave field from speaker waves.html sound water May 9 9:26 AM 28

29 tuning forks: modes.html Modal Analysis of an Acoustic Folk Guitar Vibrational Modes of a Racquetball Racket May 9 7:00 AM 29

30 Reflected sound wave all the way down May 9 9:43 AM 30

31 in middle of graph are called "phons" They relate a sound a any frequency to a 1000 Hz sound at db's May 10 7:24 AM 31

32 May 9 9:51 AM 32

33 May 10 7:51 AM 33

34 3) Quality Harmonic Content Determined by 1 number, 2 placement, and 3 intensity (amplitude) of harmonics present in the sound May 8 6:58 AM 34

35 The top graph is the tone of a wooden organ pipe The bottom graph is the same two tones played by my computer! The quality of the wooden organ pipe is enhanced by the added harmonic. May 8 6:59 AM 35

36 trumpet french horn clarinet (I can't play!) May 13 10:42 AM 36

37 Clarinet May 18 6:33 AM 37

38 ratio: name example: 2:1 2/1 octave 800 Hz/400Hz 2:3 2/3 perfect 400 Hz/600Hz fifth 3:4 3/4 perfect 900Hz/1200Hz fourth 4:5 4/5 major 200 Hz/250Hz third May 13 9:59 AM 38

39 Here's what sound waves look like. The caption reads, "A visible pattern of sound waves. This new technique of studying sound demonstrates the focusing effect of an acoustical lens on sound waves issuing from the horn at extreme left. Wave pattern is produced by a scanning technique..." Bell Telephone Laboratories (external link) < photograph, from the book The First Book of Sound: A Basic Guide to the Science of Acoustics by David C. Knight, Franklin Watts, Inc. New York (1960). p. 80 Sound waves are acoustic waves, with no electrical component. They are simply vibrations in the air, a physical pressure made by the utterance of the speaker. In somewhat challenging yet elegant writing, A.T.&T. once described sound in these terms, "Audible sound is thus defined as a disturbance in the atmosphere whereby a form of wave motion is propagated from some source at a velocity of 1,075 feet per second, the transmission being accomplished by alternating condensations and rarefacations of the atmosphere in cycles having a fundamental frequency ranging somewhere between 16 per second and 32,000 per second." Principles of Electricity applied to Telephone and Telegraph Work, American Telephone and Telegraph. C.F. Myers, Supervisor of Instruction. Murray Hills, New Jersey? p.66 May 8 8:41 AM 39

40 May 8 10:17 AM 40