Fundamentals of Sound Measurement-1

8/18/2019 Fundamentals of Sound Measurement-1

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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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Fundamentals of Sound Measurement-1