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Fundamentals ofNoise and
Measurement
By
PREPARED BY,ANKIT J. DESAI
MED, CGPIT, UTU, BARDOLI.
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Sound Measurement
• 1) Sound Pressure
Referene !a"ue# $.$$$$% &'m%
($.$$$% ) *ar
• 2) Sound Power
Referene +a"ue# $#%
-att
• ) Sound Intensit!
Referene !a"ue# $#% -att'm%
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Sound PressureMeasurement
• Sound ressure /s e0ressed /n terms"o1est sound ressure 12/2 t2enorma" ear an detet as a referene
ressure, and /t /s 3/+en *y SoundPressure "e#el $SP")%
SPL( %$Lo3$ dB
•
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Sound Po1er Measurement
• Sound o1er /s e0ressed /n terms"o1est sound o1er 12/2 t2enorma" ear an detet as a refereneo1er, and /t /s 3/+en *y SoundPower "e#el $S&")%
S-L( $Lo3$ dB
•
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Sound Intens/tyMeasurement
• Sound Intens/ty /s e0ressed /n terms"o1est sound Intens/ty 12/2 t2enorma" ear an detet as a referene
Intens/ty, and /t /s 3/+en *y SoundIntensit! "e#el $I")%
IL( $Lo3$ dB
•
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Com*/n/n3 Sound Le+e"s
• 5 Addition of sound "e+e"s
• %5 Su'tra(tion of sound "e+e"s
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Com*/n/n3 Sound Le+e"s• C2art for Add/t/on and Su*trat/on of sound
"e+e"s6#
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Add/t/on of Sound Le+e"s
• Corret/on fator de/des on t2e *ase of d/7erene *et1eent1o sound "e+e"s 12/2 are added.
• Ta*"e for se"et/on of orret/on fator6#
8 SPL 1 2 * + , - / 1 anda'o#e
0orre(tion Fa(tor
9 %.: % % .: $.:
$.: $
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-e/32t/n3 &et1or;s
• Bas/ t2ree tyes6# A, and 0 1e/32tednet1or;s
A &ei34ted net1or;6 Des/3ned to 3/+e resonse from +ery "o1 to 2/32
sound "e+e"s
&ei34ted net1or;6 Des/3ned to 3/+e resonse of ::#
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Re+er*erat/on T/me =RT5
A((ordin3 to Sa'ine5s formula6
7T8
&4ere6 98 9olume of t4e en(losure
a8 Total a'sor:tion of t4e en(losure
$a8 Area;
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-e/32t/n3 &et1or;s
• -2en -e/32t/n3 net1or;s ro+es des/ra*"e, (orre(tionmust 'e added to linear readin3s to o'tain wei34tedreadin3 for a :arti(ular fre=uen(!.
• A# 1e/32t/n3 net1or; orret/ons are as 3/+en *e"o16#
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-e/32t/n3 &et1or;s
• Pro'lem# G/+en t2e sound setrums2o1n *e"o1, >nd t2e "/near =un1e/32ted5tota" sound ressure "e+e" /n dB and t2en
A#1e/32ted tota" sound ressure "e+e" /ndB.
Fre=uen(!'and $>?)
1.+
, 12+ 2+ + 1
2
*
Soundressure"e+e" =dB5
?: ?: ?$
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Sound Le+e" Meter
• T2e most ommon and on+en/ent instrument formeasurin3 sound le#el of a sound @eld.
• T2e e"ements of SLM6#
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Sound Le+e" Meter
• T2e +ar/ous 3rades of S"M are as *e"o16#
T!:e or La*oratory, referene, a"/*rat/on ofot2er SLM
T!:e 1 or 3enera"# >e"d urose
)T!:e 2 # or 3enera"# >e"d urose
)T!:e or re"/m/nary /n+est/3at/on
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Sound Le+e" Meter
• To aommodate t2e 2enomenon of+ar/at/on or utuat/on /n sound "e+e", SLM/s ro+/ded 1/t2 "e+e" resonses, 12/2
are6#
• 5 fastB resonse T/me onstant /s $$mse.
• %5 slowB resonse T/me onstant /s se.
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Sound Le+e" Meter
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Ota+e Band
f 28 2n f 1
&4ere6
f 2 8 4i34er (enter
fre=uen(!
f 1 8 "ower (enter fre=uen(!
andwidt4C
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Ota+e Band
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Ota+e Band
• 11 $standard) (ta#e 'ands
T2e aud/o setrum from F %$ Hz to F %$ KHzan *e d/+/ded u /nto F ota+e *ands.
• (ta#e 'ands T2e aud/o setrum from F %$ Hz to F %$ KHzan *e d/+/ded u /nto F % ota+e *ands.
• 1 (ta#e 'ands
T2e aud/o setrum from F %$ Hz to F %$ KHzan *e d/+/ded u /nto F 9 ota+e *ands.
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Ota+e Band• 11 $standard) (ta#e 'andsLo1er and /32er enter freHuen/es are 3/+en *y,
Fnlow 8 f n 212 , Fn4i34 8 212 ; f n
• (ta#e 'andsLo1er and /32er enter freHuen/es are 3/+en *y,
Fnlow 8 f n 21* , Fn4i34 8 21* ; f n
• 1 (ta#e 'ands
Lo1er and /32er enter freHuen/es are 3/+en *y,
Fnlow 8 f n 21, , Fn4i34 8 21, ; f n
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reHueny Ana"ys/s
Pro'lem /nd out t2e Band1/dt2 =B-5of ', J and '9 Ota+e *and.
Pro'lem
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