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TRANSCRIPT
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Chapter 16
Sound
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Sound Waves•
Sound is longitudinal pressure(compression) waves
•
Range of hearing: 20 ! to 20"000 !FREQUENCY DEMO
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Speed of Sound
Liquids and Gases: B is bulkmodulus, is mass!olume
Solids: Y is Youn"#s modulus
$$% ms is ! a& '( C)* is &+e absolu&e &eme-a&u-e.
v = B ρ
v = Y
ρ
vair = (331 m
s
) T
273 K
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#$ample 16%1/o+n B-o0n +i&s a s&eel -ail-oad -ail 0i&+ a +amme-.
Be&s1 B-o0n, s&andin" one mile do0n &+e &-a2k, +ea-s&+e ban" &+-ou"+ &+e 2ool $3
°
F ai- 0+ile +e- &0insis&e- Boosie is l1in" ne4& &o +e- and +ea-s &+e ban"&+-ou"+ &+e s&eel b1 la2in" +e- ea- on &+e &-a2k.
D5*5: Ys&eel63.'4%'%% 7a, s&eel689' k"m$
;+a& is &+e &ime di
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&ntensit' of Sound Waves
S? uni&s a-e ;m3
7o0e-
5-ea
?n&ensi&1 is -oo-&ional &o squa-e
o< amli&ude @-essu-e modula&ionA
I = ∆ E A ∆t
= P A
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&ntensit' Range for uman earing
*+-es+old o< ea-in"• %'%3 ;m3• 7 %'%' a&m
*+-es+old o< 7ain• %.' ;m3
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eciel ScaleSensa&ion is lo"a-i&+mi2
• ?' is &+-es+old o< +ea-in" @' dBA• *+-es+old o< 7ain is &+e-e
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&ntensit' vs% &ntensit' *evel• ?N*ENS?*Y is 75, ;m3 • ?N*ENS?*Y LEFEL is in de2ibels @dimensionlessA
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Sound *evel emo
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#$ample 16%2
+ nois' machine in a factor' produces a soundwith a level of ,0 d-% ow man' machines
can the factor' house without e$ceeding the100.d- limit/
aA %3. ma2+inesbA 3' ma2+ines
2A %'' ma2+ines
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Spherical Waves
#nerg' propagates
euall' in alldirections
⇒ I = P
4π r 2
I 1
I 2
= r 2
2
r 12
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#$ample 16%
+ train sounds its horn as it approaches anintersection% he horn can 3ust e heard at alevel of 40 d- ' an oserver 10 5m awa'%
reating the horn as a point source and neglect
an' asorption of sound ' the air or ground"
a) What is the average power generated ' thehorn/
) What intensit' level of the horns sound is
oserved ' someone waiting at an
aA %3 ;
bA H dB
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#$ample 16%7
BoIo Bob bu1s a 3'; &-ain 0+is&le and
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oppler #8ect
5 2+an"e in &+e
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oppler #8ect" 9oving server
;+en no& mo!in",
;+en mo!in",
Fig 14.8, p. 435
Slide 12
f = v λ
f ' = (v + vobs ) λ
ƒ' = ƒ v + vo
v
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&f oserver moves awa':
Fig 14.9, p. 436
Slide 13
ƒ' = ƒ v − vo
v
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#$ample 16%4
Ma-1 is -idin" a -olle- 2oas&e-. e- mo&+e- 0+o is
s&andin" on &+e "-ound be+ind +e- 1ells ou& &o +e- a& a$ msA
;+a& is Ma-1#s seed=
38.> ms
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oppler #8ectSource in 9otion
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oppler #8ectSource in 9otion
λ ' = λ − vsT
= λ − vsλ
v= λ 1− vs v( )
f ' = vλ '
f ' = f v
v − vs
′λ
λ
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oppler #8ect" Source in 9otion
5-oa2+in" sou-2e:
Sou-2e lea!in":
f ' = f v
v − vs
f ' = f v
v + vs
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#$ample 16%6
5n &-ain +as a b-ass band la1in" a son" on a ms, a e-son on&+e la&
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Shoc5 Waves (Sonic -ooms)
;+en &+e sou-2e !elo2i&1 a-oa2+es &+e seed o< sound,
Fig 14.11, p. 439
Slide 15
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+pplication: speed radar
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+pplication: weather radar
Bo&+ +umidi&1 @-e
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oppler #8ect:-oth server and Source 9oving
S0i&2+ a-o-ia&e si"ns i< obse-!e-o- sou-2e mo!es a0a1
ƒ' = ƒ v ± vov ± vs
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#$ample 16%;
+t rest" a cars horn sounds the note +(770 !)% he horn is sounded while thecar moves down the street% + ic'clistmoving in the same direction at 10 m
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#$ample 16%,c
5 &-ain +as a 0+is&le 0i&+ a
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>R
• 16% 1.4? 16.1? 16.,? 16.77.7;