Sound waves are produced by vibrating objects and their characteristics include pitch, which can be manipulated through illusions like Shepard tones, and speed which varies by medium and can exceed the speed of sound producing a sonic boom. The intensity of sound decreases with the inverse square of distance from the source and is perceived logarithmically in decibels with higher decibel levels associated with louder sounds.

2. • Production
–Vibrating Objects
Sound Waves
• Tuning fork
–Compression
–Rarefaction
• What type of wave is sound?

4. • Characteristics
– Pitch
• Shepard tone (auditory illusion)
Sound Waves
Superposition of waves an octave
apart. Makes it sound like the pitch is
constantly increasing or decreasing.
http://en.wikipedia.org/wiki/Shepard_ton
• Doppler Effect
http://en.wikipedia.org/wiki/Doppler_
effect
– Human Hearing
– 20-20,000 Hz

5. – Human Hearing
– 20-20,000 Hz
• Infrasonic
• Ultrasonic
• http://biertijd.com/mediaplayer/?
itemid=19448*
• http://www.school-for-
champions.com/science/sound_tra
veling_faster.htm

6. • Characteristics
–Speed of Sound
Sound Waves
• Medium
–Closeness of particles – closer
particles = ↑velocity
–Temperature – ↑Temp, ↑v
• Supersonic
–Sonic boom
–http://www.soundboard.com/sb/
Sonic_Boom_Sounds

7. Power
Intensity =
4π r 2
• Relationship between distance
Intensity
from source and intensity?
• Relative intensity (loudness)
– Decibels (dB)
• Logarithmic scale
• 10dB  20dB increase of 10X

8. Intensity (W/m2) Decibel level (dB) Examples
1.0x10-12 0 Threshold of hearing
1.0x10-11 10 Rustling leaves
1.0x10-10 20 Quiet whisper
1.0x10-9 30 Whisper
1.0x10-8 40 Mosquito buzzing
1.0x10-7 50 Normal conversation
1.0x10-6 60 Air conditioning at 6 m
1.0x10-5 70 Vacuum cleaner
1.0x10-4 80 Busy traffic, alarm clock
1.0x10-3 90 Lawn mower
1.0x10-2 100 Subway, power motor
1.0x10-1 110 Auto horn at 1m
1.0x100 120 Threshold of pain
1.0x101 130 Thunderclap, machine gun
1.0x103 150 Nearby jet engine

9. • Natural Frequency
–Resonance
• Tacoma Narrows Bridge
Other Stuff
• http://archive.org/details/SF12
1
• Hearing
– Eardrum
– Hammer, anvil, stirrup
– Cochlea
– Auditory nerve

10. • Natural Frequency
–Resonance
• Tacoma Narrows Bridge
Other Stuff
• http://archive.org/details/SF12
1
• Hearing
– Eardrum
– Hammer, anvil, stirrup
– Cochlea
– Auditory nerve