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Element B6 / 3

Measurement and Assessment of Noise

Instruments Used for Measurement

Types of Sound Pressure Level (SPL)

Meter

Type 0 Vary accurate. Used as lab reference std. High std of

tolerance over wide freq range. Not used “in the field”

Type 1 In labs or the field, high precision

Type 2 General Field meter

Type 3 Basic level indicator. Shows if exceeded levels. Least

accurate.

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Instruments Used for Measurement

Types of Sound Pressure Level (SPL)

Meter

Noise surveys – should use at least type 2

Readings at A weighted L Aeq

C weighted max peak SP to above 140 dB(C)

Ear protection and control assessments

Octave band anaylsis feature with above

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Methodology

SPL (La)

A weighted intensity of sound at given moment and

position

Equivalent cont. SPL (L Aeq)

Avg measure over reference period

dB(A)

Peak Pressure Level

CNWR exposure limit 140dB(C)

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Methodology

Ideally

Take readings at persons ear

Most work situations –

Personal portable device

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Calibration

Field calibration

At time of use

Verification calibration

Every 2 years

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Terminology

L EP,d

Daily personal noise exp level

LAeq

Equivalent A weighted continuous sound level

LA

A weighted SPL, dB(A)

LC

As above, dB(C)

L WA

A weighted Sound POWER level, dB(A)

Octave band

Band of freq, Hz

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LEP,d

True average level over 8 hrs

Taken from LAeq

Use HSE Ready Reckoner Calc Table

Different levels throughout shift

Prioritise higher level tasks / highest exp points (HSE)

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LEP,w

True average level over a working

week

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L AEQ

Noise which varies with time

A weighted average

To maintain L AEQ when SPL x 2 (

+3dB)

Exposure time must be halved

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Frequency Analysis

Noise source measured at freq bands

Octave band = highest freq is twice

lowest freq

Band denoted by centre freq. (i.e. 1kHz)

Measure in all bands to match noise

source to personal hearing protection

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Background Noise

Any sound other than that being measured

Heating, vent, aircon, other equip, traffic etc.

Measuring :

Background noise must be at least 3 dB less than source

Correction level

Measure level with source running

Measure background noise with source off

Calc diff. if less than 3 dB then too high for acc. Measurement

If between 3 and 10 dB then correction

If greater than 10 dB then no correction

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Legal Limits

CNWR Reg 4

Lower exposure action values

Daily or weekly personal 80 dB(A)

Peak SPL 135 dB(C)

Upper exposure action values

Daily or weekly personal 85 dB(A)

Peak SPL 137 dB(C)

Exposure Limit Values

Daily or weekly personal 87 dB(A)

Peak SPL 140 dB(C)

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