ThermoFluid Lab (Sound Measurment)

7/24/2019 ThermoFluid Lab (Sound Measurment)

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Notre Dame University (Louaize)

Faculty of Engineering

Department of Mechanical Engineering

MEN 37

!hermo"Flui# La$oratory

Fall %&'

oun# Measurement

*roup num$er+ %

,repare# $y+

Micheline aa# -D+ %&'37'.

u$mitte# to+

/issam Daou

Date of e0periment+

Fri#ay1 2cto$er 1 %&'

Date of su$mission+

Fri#ay1 2cto$er '1 %&'

Abstract


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ince human $eings are al4ays su$5ecte# to #ifferent soun#s 4herever they are1 it is necessary to

#etermine soun# level in or#er to ensure humans6 safety1 an# conseuently #etermine a

ma0imum e0posure time to high levele# soun#s8 -n this conte0t1 a cali$rate# Lutron Digital

soun# meter L 9&''1 an instrument to measure soun# levels1 4as use# $y a group of stu#ents to

measure soun# levels in #ifferent locations in Notre Dame University Louaize (:ou; Mos$eh)8

!hen1 a general overvie4 on the soun# 4aves an# their properties is #iscusse#8 % ta$les in

a##ition to a num$er of euations are sho4n an# specially that of the soun# level8


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Introduction

,ro$lem+

-f a soun# reaches . #> or more1 it can cause permanent #amage to human hearing8 !he amount

of time a person listens to a soun# is also important8 < human $eing 4oul# have to listen to an .

#> soun# for over . hours to cause hearing #amage1 $ut soun#s measuring '%& #> can instantly

cause #amage8


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Mechanical 4aves are 4aves that reuire a material me#ium to e0ist8 !hey are of t4o types+

Transverse wavesan# longitudinal waves.oun# 4ave is a mechanical 4ave that is roughly

#efine# as any longitu#inal 4ave8

!he spee# of traveling soun# 4aves1 pressure amplitu#e1 an# #isplacement amplitu#e are some

of the main physical characteristics of soun# 4aves8


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of spea;ing of the intensityI of a soun# 4ave1 it is much more convenient to spea; of its sound

level 1 #efine# as+

=(10dB ) log

I

I0 8 (e8 3)

ere #> is the a$$reviation of #eci$el 4hich is the unit of soun# level1I0 is a stan#ar# reference

intensity ( '&A'%/"m%) chosen $ecause it is near the lo4er limit of the human range of hearing8

ome common soun# levels in #eci$els are sho4n in the follo4ing ta$le+

Home Work Recreation

& refrigerator

& B 7 air con#itioner

coffee percolator

B 7 #ish4asher

B .& alarm cloc;

7 B . flush toilet

.& ringing telephone

9& uiet office1 li$rary

& large office

electric #rill

'&& factory machinery

'%& chain sa41 hammer

on nail

''& po4er sa4

7& free4ay traffic

. heavy traffic1 noisy

restaurant

& truc;1 shoute#

conversation

''& car horn

''% personal cassette

player on high

5


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-t shoul# $e

also note#

that

accor#ing to

the National

-nstitute for 2ccupational afety an# ealth (N-2) an# the enters for Disease ontrol an#

,revention (D) for every 3 #> soun# level over .er #>1 the permissi$le e0posure time is cut

in half $efore #amage to human hearing can occur8 !he follo4ing ta$le represents the prece#ing

information8

Sound level (d! Permissible e"posure time

'' &89.7 minutes ( 3& secon#s)

''% &837minutes ( ' min)

'& '8.7 minutes (G % min)

'& 387 minutes (G 9 min)

'&3 78 minutes

'&& ' minutes

7 3& minutes

9 ' hour

' % hours

.. 9 hours

. . hours

.% ' hours

Table 2:Recommended permissile e!posure time "or continuous time weig#ted average noise

6

Table 1: Some sound levels $d%&


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Results

Table 2 sho4s some soun# levels measure# e0perimentally in #ifferent locations insi#e the

university+ from the la$oratory through the li$rary an# the cafeteria to the insi#e of an un#er

ongoing construction $uil#ing1 an# finally to the par;ing8

#ocation Sound level (d!

Large li$rary .87

Huiet office '89


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traffic 798

,ersonal cassette player on high '&%83

ar horn 98

Flush toilet .'83Electric #rill '&&8'

houte# conversation .3

,o4er sa4 '&78

ammer on nail 38

!he previous

#ata sho4n

in Table 3 is

represente#

in Graph 1

for the ease of rea#ing an# comparing the collecte# values8

8

Table 3: Some e!perimentall' measured sound levels $d%&


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9

Graph 1: Some sound levels measured e!perimentall' in di""erent locations


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58.7

51.4

61.7

82.481.678.1

68.2

83.4

74.474.5

102.3

94.9

81.3

100.1

83

107.5

93.5

!he measure# soun# levels varies from a minimum value of '89 #> in a uiet office to a

ma0imum value of '&78 #> for a po4er sa48 Most of the measure# levels are less than . #>

(the minimum value at 4hich hearing #amage may occur)8 ,laying music on high an# stan#ing in

a 4or;place may cause some hearing #amage (soun# level higher than . #>)8

$iscussion and Conclusion

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-n or#er to get a general i#ea a$out the results an# the theoretical values1 e0perimentally

measure# soun# levels 4ith their theoretical values are all sho4n in the graph $elo48

58.7

51.4

61.7

82.4 81.678.1

68.2

83.4

74.474.5

102.3

94.9

81.3

100.1

83

107.5

93.5

50

40

50

80

55 5550

85

6570

112 110

75

9590

110

120

75 7580

85

Experimental SL Theoretical SL Theoretical SL

>y e0amining Graph 21 one can notice that the e0perimental an# theoretical soun# levels are

appro0imately close8

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Graph 2:(!perimentall' measured sound levels wit# t#eir corresponding t#eoretical values


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!he e0perimental soun# levels of the alarm cloc;1 #ish 4asher1 an# air con#itioner fall e0actly in

their correspon#ing theoretical range8 E0cept for the hammer on nail1 the refrigerator1 an# the

coffee percolator1 the other soun# levels are close to the theoretical values8

#ocation %"perimental Sound

Theoretical Sound

& %rror

Large li$rary .87 & '789I

Huiet office '89 9& %.8I


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>y chec;ing

Table41 the

percentage of

error is

foun# to $e

#ifferent+ some places it is small 4hile in other places it is high8

!o fin# the percentage of error for each location1 the follo4ing euation has $een use#+

%Error=

|experimental valueaccepted value|

accepted value 100

(e8 9)

!he I error is high (J'I) for the li$rary1 office1 coffee percolator1 refrigerator1 an# hammer on

nail8

o4ever the average I error is '%83 I8 -t is slightly high $ut most of the results are accurate an#

precise8

For the locations 4ith high I error1 this is #ue to the follo4ing reasons+

!he coffee percolator an# the refrigerator are locate# in the university cafeteria8 !he error

in the soun# level 4as cause# $y the noise of the stu#ents8

!he li$rary an# the office $oth inclu#e air con#itioners8


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place have high level soun#s an# people shoul# re#uce their e0posure time to such soun#s8

ThermoFluid Lab (Sound Measurment)

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