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Ch 16 Sound and Hearing © 2005 Pearson Education

16.1 Sound Waves © 2005 Pearson Education Sound is a longitudinal wave in a medium Audible range of human ear is 20 to 20000Hz

© 2005 Pearson Education Gauge pressure

© 2005 Pearson Education Different ways to describe a sound wave

© 2005 Pearson Education In a sinusoidal sound wave the max pressure variations are 3.0*10 -2 Pa above the atmospheric pressure. Find the max displacement if frequency is 1000Hz. Given speed of sound is 344m/s and bulk modulus is 1.42*10 5 Pa ANS: ANS:

16.2 Speed of Sound Waves © 2005 Pearson Education

Speed of longitudinal wave © 2005 Pearson Education

What is the speed of longitudinal waves in a lead rod? ANS: ANS: © 2005 Pearson Education

16.3 Sound Intensity intensity of a sinusoidal sound wave definition of sound intensity level © 2005 Pearson Education

16.4 Standing Sound Waves and Normal Modes © 2005 Pearson Education

Displacement node: where particles of the fluid have zero displacement Displacement node: where particles of the fluid have zero displacement Displacement antinode: where particles of the fluid have maximum displacement Displacement antinode: where particles of the fluid have maximum displacement A pressure node is always a displacement antinode, and a pressure antinode is always a displacement node. © 2005 Pearson Education

Example A directional loudspeaker aims a sound wave of wavelength λ at a wall in the below fig. At what distance from the wall could you stand and hear no sound at all? A directional loudspeaker aims a sound wave of wavelength λ at a wall in the below fig. At what distance from the wall could you stand and hear no sound at all? © 2005 Pearson Education

Open pipe © 2005 Pearson Education

Open pipe © 2005 Pearson Education

open pipestopped pipe © 2005 Pearson Education Stopped pipe

16.5 Resonance © 2005 Pearson Education Resonance occur when the driving frequency equal to the one of the normal-mode frequency of the system

16.6 Interference of Waves © 2005 Pearson Education Constructive interference Destructive interference

© 2005 Pearson Education Path different is 0, λ, 2λ…… Path different is λ/2, 3λ/2, 5λ/2...

16.7 Beats beat frequency © 2005 Pearson Education

16.8 The Doppler effect © 2005 Pearson Education Moving listener and stationary source

Moving source and moving listener © 2005 Pearson Education

Example If the siren is at rest and the listener is moving toward the left at 30 m/s, what frequency does the listener hear? If the siren is at rest and the listener is moving toward the left at 30 m/s, what frequency does the listener hear? ANS:

16.9 Shock Waves shock wave © 2005 Pearson Education

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