Sound W

aves

• Production–Vibrating Objects

•Tuning fork–Compression

–Rarefaction

•What type of wave is sound?

Sound W

aves

• Characteristics–Pitch

• Shepard tone (auditory illusion)Superposition of waves an octave apart. Makes it sound like the pitch is constantly increasing or decreasing.

http://en.wikipedia.org/wiki/Shepard_tone• Doppler Effect

http://en.wikipedia.org/wiki/Doppler_effect

–Human Hearing–20-20,000 Hz

• Infrasonic• Ultrasonic

–Human Hearing–20-20,000 Hz

• Infrasonic• Ultrasonic

• http://biertijd.com/mediaplayer/?itemid=19448*

• http://www.school-for-champions.com/science/sound_traveling_faster.htm

Sound W

aves

• Characteristics–Speed of Sound

•Medium–Closeness of particles – closer particles = ↑velocity

–Temperature – ↑Temp, ↑v

•Supersonic–Sonic boom

–http://www.soundboard.com/sb/Sonic_Boom_Sounds

Intensity

• Relationship between distance from source and intensity?

• Relative intensity (loudness)–Decibels (dB)

• Logarithmic scale

• 10dB 20dB increase of 10X

24

PowerIntensity

r

Intensity (W/m2) Decibel level (dB) Examples1.0x10-12 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

Other S

tuff

• Natural Frequency–Resonance

•Tacoma Narrows Bridge•http://archive.org/details/SF121

• Hearing– Eardrum– Hammer, anvil, stirrup– Cochlea– Auditory nerve