particle motion
l
http://positron.ps.uci.edu/~dkirkby/music/html/demos/PlaneWave/SoundWave.ht
m
sound waves and the ear drum
http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/waves/edl.html
sound as a pressure wave
http://www.glenbrook.k12.il.us/gbssci/phys/Class/sound/u11l1c.html
Title: May 9 ­ 9:02 AM (1 of 29)
Sound
the speed of sound
v
s
= 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
Title: May 9 ­ 10:16 AM (2 of 29)
Sound is a longitudinal (compressional) wave
the base wave equation is: characteristics:
1) Frequency
v
s
= fλ
(pitch)
humans hear between 20 Hz ­ 20,000 Hz
Title: May 9 ­ 10:18 AM (3 of 29)
Difference between a high frequency sound and a low frequency sound.
Title: May 9 ­ 12:07 PM (4 of 29)
Title: May 9 ­ 10:39 AM (5 of 29)
Difference in Intensities
Title: May 9 ­ 12:42 PM (6 of 29)
Title: May 9 ­ 12:07 PM (7 of 29)
Difference in amplitudes
Title: May 9 ­ 12:08 PM (8 of 29)
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?
2
2
I = P/ 4πr = 25 W/ 4π(10m) I = .02 W/m
Title: May 9 ­ 10:46 AM (9 of 29)
2
Title: May 9 ­ 11:24 AM (10 of 29)
Title: May 9 ­ 11:28 AM (11 of 29)
sound at threshold of pain
Title: May 10 ­ 8:09 AM (12 of 29)
A stereo boasts that it can reproduce sounds between 17 hz and 17,000 Hz with as little as a 5db difference in loudness. What is the the ratios of the intensities of the sounds?
Title: May 10 ­ 8:10 AM (13 of 29)
P = power gradient
o
Title: May 10 ­ 8:16 AM (14 of 29)
Title: May 10 ­ 8:26 AM (15 of 29)
Title: May 10 ­ 8:28 AM (16 of 29)
sound wave field from speaker
http://www.mediacollege.com/audio/01/sound­waves.html
http://www.kettering.edu/~drussell/Demos/rad2/mdq.html
Title: May 9 ­ 9:26 AM (17 of 29)
Reflected sound wave
http://www.phy.ntnu.edu.tw/java/propagation/propagation.html
Title: May 9 ­ 9:43 AM (18 of 29)
Title: May 9 ­ 9:07 AM (19 of 29)
Title: May 11 ­ 8:24 AM (20 of 29)
Doppler Shift
http://www.kettering.edu/~drussell/Demos/doppler/doppler.html
car horn
still
slower than v
v
faster than v
s
s
s
Title: May 9 ­ 9:49 AM (21 of 29)
Title: May 10 ­ 9:33 AM (22 of 29)
bullet at mach 1.01, note shock wave just in front of the bullet
Title: May 10 ­ 9:33 AM (23 of 29)
bullet at mach 2.45
Title: May 10 ­ 9:35 AM (24 of 29)
Title: May 9 ­ 9:49 AM (25 of 29)
Title: May 9 ­ 9:50 AM (26 of 29)
Title: May 10 ­ 7:51 AM (27 of 29)
10 ­ 120 in middle of graph are called "phons"
They relate a sound at any frequency to a 1000 Hz sound at___db's
Title: May 10 ­ 7:24 AM (28 of 29)
Title: May 9 ­ 9:51 AM (29 of 29)