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Human Factors Laboratory

Noise

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Noise

Definitions

Unwanted sound

Auditory stimuli carrying no information relevant

to current tasks

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Measurement

Units

Sound Pressure Level: amplitude of the pressure

fluctuations.

The weakest sound: 20 Pa = 0 dBPa x 10 = dB + 20

Measured in Pascal, but could be changed into

decibels (dB)

Sound level meters

Definitions

A, B, C scales

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The smallestchange: 3 dB /1.5 kalinya

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A, B, and C Scales

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Physiological Effects

Short Term Effects

Startle response

Long Term Effects ( > 95 dBA, > 10 yrs)

Hypertension

Headaches

Irritability

Sleep disorders

etc.

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Annoyance (2)

Objective Scales

Equivalent Sound Level (Leq)

Day-Night Level (Ldn)

Ldn= Leqfor 24 hours period with correction

add 10 dB for 2200 - 0700 hrs

Community Response

Ldn (dBA) Response

50 - 60 none or sporadic60 - 70 wide spread complaints

70 - 75 threats of legal action

75 - 80 vigorous action

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OSHA Standards: Continuous Noise

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Noise Dosage

total (daily) dose = sum of partial doses

Requirement: total dose < 1.00

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Example

Worker exposed to 90 dBA for 4 hours,105 dBA for 30 minutes. Within dosage limits?

4 hr @ 90 dBA = 4 / 8 = 0.5

0.5 hr @ 105 dBA = 0.5 / 1 = 0.5Total dosage = 0.5 + 0.5 = 1.0

Since 1.0 < 1.0, dosage is OK

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Annoyance (1)

FactorsSubjective Scales, e.g.

noticeable

intrusive

annoying

very annoying

unbearable

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Influence of Environment

Wind Humidity

Temperature

Ambient pressure

Vibration Magnetic fields

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Noise control

Acoustic absorption, insulation Damping

Design (machine or workplace)

Isolation

Maintenance

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Applications

Noise and stress Noise and blood pressure

Noise and music

Not related to output

Related to output for boring task Noise and satisfaction

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Vibration

Vibration effect: amplitude, frequency

Classification of vibration:

Whole or major portion of the body surface (e.g.:

earthquake)

Transmitted through supporting area (e.g.: buttocks of a

person driving truck, feet of a person standing by a

shakeout facility)

Localized body area (e.g.: hand when operating power

tools)

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Limit

Around 4 m/s for 8 hr 60 s (minimum measurement time)

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Effect: headache, vision problem, lossappetite, bone atrophy, arthritis, occludeblood flow, affect nerves, white fingersyndrome

To reduce: Modifying the speed, motion

Maintain the equipment

Place anti-vibrating equipments to lessen vibration

Implement suspension system

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Take home Quiz (Android apps)

Download apps Noise Meter, rekam kebisingan dibeberapa tempat (2 menit):

Di pinggir jalan yang ramai (Margonda)

Di dalam KRL

Di persimpangan jalan dg KRL (ketika sirene berbunyi)

Download apps Vibrometer, rekam vibrasi di lokasiberikut dalam kondisi jalan (2 menit):

Di dalam KRL

Di dalam angkot/metromini

Di dalam mobil pribadiAnalisis singkat apakah rata-rata noise dan vibrasi yang

dihasilkan sudah melebihi ambang batas atau belum.

Dikumpulkan softcopy, tanggal 26 Mei 2014