Chapter 15 The Nature of Sound What is Sound??? Sound is a Longitudinal Wave traveling through matter

Embed Size (px)

Text of Chapter 15 The Nature of Sound What is Sound??? Sound is a Longitudinal Wave traveling through...

  • Slide 1
  • Slide 2
  • Chapter 15
  • Slide 3
  • The Nature of Sound What is Sound??? Sound is a Longitudinal Wave traveling through matter.
  • Slide 4
  • Longitudinal Waves Matter vibrates in the same direction as the wave travels.
  • Slide 5
  • Slide 6
  • Longitudinal Waves Compression Rarefaction
  • Slide 7
  • Slide 8
  • Sound from a Tuning Fork
  • Slide 9
  • Speed of Sound Sound is transmitted through matter. The Velocity of Sound depends on the matter that carries it.
  • Slide 10
  • Sound travels at a velocity of 332m/s in air at 0 C. Sound travels faster through warm air than through cold air. The velocity of sound increases about 0.6m/s for each degree in temperature. Sound travels much faster through liquids and solids than through gases. At 20 C sound travels at 344m/s.
  • Slide 11
  • Comparing Media MediaSpeed of Sound Air at 0C331m/s Air at 20C343m/s Water at 25C1493m/s Sea Water at 25C1533m/s Iron at 25C5130m/s Rubber at 25C1550m/s
  • Slide 12
  • Human Hearing Frequency of Sound 20 Hz to 20,000 Hz. Sound above 20,000 Hz - Ultrasonic Sound less than 20 Hz Subsonic (Infrasonic)
  • Slide 13
  • Frequency is Pitch
  • Slide 14
  • Detection of Pressure Waves
  • Slide 15
  • Ear Drum
  • Slide 16
  • Intensity and Loudness Intensity of Sound Depends on the amplitude of the wave. Loudness Describes a persons response to sound intensity.
  • Slide 17
  • Loudness is measured in Decibels(dB) For every 10dB change the sound doubles!! 70dB is twice 60dB 80dB is four times 60dB
  • Slide 18
  • Faintest Sound Heard0dB Whisper15dB Rustling Leaves20dB Purring Cat25dB Average Home50dB Vacuum Cleaner75dB Noisy Restaurant 80dB Power Mower100dB Chain Saw115dB ------Painful ------- 120dB Jet Plane Taking Off150dB
  • Slide 19
  • Interference Constructive Interference Occurs when the compressions and rarefactions of two or more waves come together. Louder Sound
  • Slide 20
  • Interference Destructive Interference Occurs when a compression of one wave arrives at the same time as a rarefaction of another wave. Quieter Sound
  • Slide 21
  • Interference Beats The result of compressions and rarefactions of two slightly different frequencies reaching your ears together. Beats
  • Slide 22
  • f 1 = 512Hz f 2 = 514Hz Beats = f 1 - f 2 Beats = 2Hz (beats/s) = 514Hz - 512Hz
  • Slide 23
  • The Doppler Effect The change in wave frequency caused by the motion of the sound source or the motion of the observer.
  • Slide 24
  • The Doppler Effect Shorter Wavelength Higher Frequency
  • Slide 25
  • The Doppler Effect Longer Wavelength Lower Frequency
  • Slide 26
  • Slide 27
  • Slide 28
  • Speed of Sound
  • Slide 29
  • Greater than the Speed of Sound
  • Slide 30
  • Homework #15-1 PP: 1-4 Page: 352 Section Review Page:355 Due: 3/12/03
  • Slide 31
  • Resonance A resonant frequency is a natural frequency of vibration determined by the physical parameters of the vibrating object.
  • Slide 32
  • Harmonics Vibrations which occur at a particular frequency is known as a harmonic.
  • Slide 33
  • First Harmonic The lowest possible frequency at which a string could vibrate to form a standing wave pattern is known as the fundamental frequency or the first harmonic.
  • Slide 34
  • First Harmonic
  • Slide 35
  • Second Harmonic
  • Slide 36
  • Third Harmonic
  • Slide 37
  • Resonance in Air Columns Closed Air Column = 4L L = 4 / 3 L = 4 / 5 L
  • Slide 38
  • Resonance in Air Columns Open Air Column = 2L L = L = 2 / 3 L
  • Slide 39
  • Example A tuning fork is placed above an open-pipe resonator in which the length can be changed. The loudest sound is heard at a length of 67cm and the next loudest was heard at 100.5cm. If the temperature of the air is 20C what is the frequency of the tuning fork?
  • Slide 40
  • Example 67cm 100.5cm (100.5 - 67)= 33.5cm 33.5cm = 233.5cm = 67cm =
  • Slide 41
  • Example = 67cm = 0.67m v@20C = 343m/s v = f f = v/ f = 512Hz f = 343m/s 0.67m
  • Slide 42
  • Homework #15-2 PP: 5-9 Page: 362 Due: 3/17/03
  • Slide 43
  • Music to Your Ears A back and forth motion is set up in a string, resulting in a regular vibration. The vibration is called a standing wave the location of the crests and troughs are always in the same place.
  • Slide 44
  • In a wind instrument, holes are opened and closed, changing the length of the vibrating column of air. This changes the size of the standing wave.
  • Slide 45
  • Noise Sound with no regular pattern or definite pitch.
  • Slide 46
  • Tone Quality The differences among sounds of the same pitch and loudness.
  • Slide 47
  • Music Musical Sounds Based on a series of notes called a musical scale.
  • Slide 48
  • The Sound Spectrum: Fundamental and Harmonics
  • Slide 49
  • Open Air Column = 2L L = L = 2 / 3 L f 1 = v/ f 1 = v/2L f 2 = v/L f 2 = 2f 1 f 3 = v/ 2 / 3 L f 3 = 3f 1
  • Slide 50
  • Fundamental Frequency First Overtone Second Overtone Third Overtone 262Hz 524Hz 786Hz 1048Hz
  • Slide 51
  • Closed Air Column = 4L L = 4 / 3 L = 4 / 5 L f 1 = v/4L f 2 = v/ 4 / 3 L f 2 = 3f 1 f 3 = v/ 4 / 5 L f 3 = 5f 1
  • Slide 52
  • Fundamental Frequency First Overtone Second Overtone Third Overtone 256Hz 768Hz 1280Hz 1792Hz
  • Slide 53
  • Harmony Notes that sound pleasing together. The ratio of the frequencies of tones that are in harmony are small whole numbers. Notes that are one octave apart. Middle C and C 524/262 = 2/1 Notes E and C 330/262 = 5/4
  • Slide 54
  • Dissonance and Consonance Dissonance combination of pitches that sound unpleasant. Consonance combination of pitches that sound pleasant.
  • Slide 55
  • Musical Intervals Octave: Two notes that have a ratio of 1:2. Example: 440Hz 880Hz one octave higher. 220Hz one octave lower.
  • Slide 56
  • Interference Constructive Interference Occurs when the compressions and rarefactions of two or more waves come together. Louder Sound
  • Slide 57
  • Interference Destructive Interference Occurs when a compression of one wave arrives at the same time as a rarefaction of another wave. Quieter Sound
  • Slide 58
  • Interference Beats The result of compressions and rarefactions of two slightly different frequencies reaching your ears together. Beats
  • Slide 59
  • f 1 = 512Hz f 2 = 514Hz Beats = f 1 - f 2 Beats = 2Hz (beats/s) = 514Hz - 512Hz
  • Slide 60
  • Homework #15-3 Practice Problem:10 Section Review Page: 367 Due: 3/18/03
  • Slide 61
  • Homework #15-4 Study Guide Due: 3/19/03 Test: 3/20/03

Recommended

View more >