Nebosh Diploma - Unit B6

Front 1

Noise

Back 1

Noise at Work Regulations 2005:

Any audible sound

Oxford English Dictionary:

A sound, especially one that is loud or unpleasant or that causes disturbance

Sound:

Vibrations or pressure changespassing through a medium, usually air

Front 2

Sound

Back 2

Front 3

Sound Intensity and Decibels

Back 3

Intensity is sound power per unit area

A measure of the flow of sound energy - units W/m2

Lowest value detected by human ear is 10-12 W/m2

Highest likely to be encountered is 1 W/m2

Very large range so Decibel (dB) used for convenience

Logarithmic scale

Usually expressed as sound pressure level

Front 4

Decibel Scale

Back 4

Threshold of pain - 130

Noisy factory - 90

Busy traffic - 70

Normal conversation - 60

Soft whisper - 20

Threshold of hearing - 0

Logarithmic scale, so increase of 3 dB means doubling of sound intensity

Front 5

Adding Decibels

Back 5

If adding similar values, add 3dB

e.g. 90dB + 90 dB = 93dB

If adding dissimilar values, use graph or table

Front 6

Frequency

Back 6

Pitch of note

Sounds usually a mixture of frequencies

Human hearing range given as 20Hz to 20KHz

Frequencies often divided into octave bands, represented by central value

Frequency important in control, and selection of hearing defenders

Front 7

Frequency - Octave Band

Back 7

Front 8

A-Weighting

Back 8

Tones of the same pressure level do not sound equally loud to the ear, nor do they have the same potential for causing hearing loss

High frequencies sound louder and are more likely to cause damage

Low frequencies sound quieter and are less likely to cause damage

A- weighting compensates for this differenceAfter A-weighting is adopted - dB(A)

Front 9

C-Weighting

Back 9

A-weighting is not appropriate at high noiselevels

Ear becomes better at hearing high/low frequencies

Almost linear response

Used for peak values - dB(C)

Front 10

Noise Dose

Back 10

Noise measurements usually averaged over a time period

Known as Leq:

L can be any length of time

Control of Noise at Work Regulations refer to Daily noise exposure:

Averaged over 8 hour period

Known as daily noise exposure or LEP,d

Also make reference to peak values

Front 11

Mechanism of Hearing

Back 11

Vibrations directed by pinna into auditory canal

Eardrum vibrates

Vibrations carried across middle ear by ossicles to cochlea

Vibrations pass through fluid in cochlea in inner ear

Detected by sensory hairs (stereocilia)

Conveyed to brain by auditory nerve

Front 12

Noise - Adverse Health Effects

Back 12

Nuisance and stress

Tinnitus

Noise induced hearing loss (NIHL)

Temporary threshold shift - reversible damage (auditory fatigue)

Permanent threshold shift - failure of her cells to respond to frequencies

Acoustic trauma

TTS & PTS (NIHL) generally occurs in the 4000hz octave band - 4K dip

Front 13

Acoustic Shock

Back 13

Sudden, unexpected loud sound through headset

May be below Action Values

No loss of hearing

Symptoms:

Early: tinnitus, dizziness, nausea

Intermediate: headaches, fatigue, anxiety

Late: hypersensitivity, anxiety returning to telephone work

Controls:

Protection devices

Reduce background noise

Prompt repair of equipment

Manual control of voice levels

Front 14

Audiometry - Basic Principles

Back 14

Routine health surveillance

Health surveillance required if risk assessment identifies risk to health

Guidance suggests this is regular exposure above upper exposure action value

Shall include test of hearing – audiometry

Used as base line assessment

Also implications in Civil Law

Front 15

Audiometry - Method

Back 15

Details given in standard (EN26189:1991)

Quiet environment

No significant noise for 16 hours previously

Pure tones played - subject presses button if heard

Software produces graph (audiogram)

Front 16

Audiometry - Audiogram

Back 16

Front 17

Audiometry - Age Related Hearing Loss (Presbycusis)

Back 17

Front 18

Audiometry - Action to be Taken

Back 18

Category & Action

1: Acceptable:

No action required

2: Mild hearing impairment:

Formal notification

Reinforcement of training and importance of controls

Good practice to issue copy of audiogram

3: Poor hearing:

Referral to medical practitioner

4: Rapid hearing loss

Referral to medical practitioner

Front 19

Control of Noise at Work Regulations (CNWR) 2005 - Regulation 4 & 5

Back 19

Reg. 4:

Exposure action values and exposure limit values

Reg. 5:

Assessment to be carried out where exposure likely to reach lower exposure action value (80 dB(A))

To cover:

Level, type, duration of exposure

Manufacturers information

Availability of alternative equipment

Results of health surveillance

Availability of PPE

Recorded and reviewed

Front 20

CNWR - Action Values

Back 20

Lower Exposure Action Value - 80 dB(A) LEP,d/Peak 135 dB(C):

Make PPE available

Provide information and training

Assessment Upper Exposure Action Value - 85 dB(A) LEP,d/Peak 137 dB(C):

Reduce ALARP by means other than PPE

Hearing Protection Zones

Health surveillance (audiometry)

Front 21

CNWR - Limit Values

Back 21

Upper Exposure Limit Value - 87 dB(A) LEP,d/Peak 140 dB(C):

Not to be exceeded

Front 22

CNWR - Limit Values Exceeded

Back 22

Exposure is not permitted above exposure limit value (87dB(A))

If exposure does occur, employer must reduceexposure to noise to below the exposure limitvalue

Identify the reason for that exposure limit value being exceeded

Modify the organisational and technical measures to prevent it being exceeded again

Front 23

CNWR - Regulation 7

Back 23

Hearing protection:

To be made available at or above lower exposure action value

Must be worn above upper exposure action value (if cannot be controlled by other means)

Hearing Protection Zones:

Designated and signage displayed

Employer to maintain PPE and ensure use SFARP (Reg 8)

Front 24

CNWR - Regulation 9 & 10

Back 24

Reg.9 - Health surveillance:

Where the risk assessment indicates that there is a risk to health

Risk to health:

If there is regular exposure above the upper exposure action value

Must include a hearing test (audiometry)

If hearing damage is identified then the employer must refer the individual to a medical practitioner.

Reg. 10:

Employer to provide information, instruction and training where lower exposure action value is reached

Front 25

CNWR - Employees Duties

Back 25

To comply with the employers arrangements for controlling noise

To use hearing protectors and noise control equipment

To take care of such equipment, and to report any defects (all Reg 8)

To co-operate with employer and attend hearing tests (Reg 9)

Front 26

Noise Measurement - Basic Principles

Back 26

Sound Level Meter:

Simple measures dB or dB(A) at a moment in time

Integrating if measures Leq

Leq - equivalent continuous noise level

Need to measure A-weighted Leq (LAeq)

Need C-weighting for peak levels

Need to be calibrated each time they are used

Front 27

Noise Measurement - Classes of Device

Back 27

Lower the class of SLM, higher the quality

Class 0 - Research

Class 1 - Laboratory/Field

Class 2 - General Field

Class 3 - Non integrating

Calibrators also different classes

Selection depends on objectives of survey

Increasing accuracy and response from

Class 3 to Class 0

Class 1 or 2 for occupational safety measurements

Front 28

Noise Measurement - Personal Dose Meters & Frequency Analysers

Back 28

Personal dose meters:

Worn by person exposed in hearing zone

Measures actual dose for referenced time period

Frequency analysers:

Measure sound pressure levels at particular frequencies

Required for accurate assessment of hearing defenders

Combination of above and accessories

e.g. storage of data, print outs, software

Front 29

Workplace Noise Survey

Back 29

Planning:

Objectives and scope

Information sources:

Previous assessments

Employees

Manufacturers information

Complaints

Selection of measuring equipment including calibrators

Battery check

Number of employees exposed/duration

Areas to be surveyed

Recording of data

Route

Safety issues/risk assessment

Front 30

The Ready Reckoner - Estimate (L108)

Back 30

Estimate of noise exposure:

Try this:

1) 30 mins spent working on a grinding machine - manufacturers info says 95dB

2) 3 hours working in yard with vehicles - check suggests 85dB

3) 1.5 hours in office - check suggests 80dB

4) 2 hours back in yard at 85dB

Front 31

Estimating LEPd - Static Measurements

Back 31

Static measurements taken at operating positions at each machine

Static measurements taken during normal operation

Sound measured as LAeq

Use integrating SLM

Note the time operator spends at each machine

Calculate using points system/HSE spreadsheet

Assess or assume insignificant exposure during breaks

Front 32

NoisePropagation

Back 32

Front 33

Effect of Distance - Inverse Square Law

Back 33

Inverse square law:

Refers to decrease in noise energy (and other energy forms) as it moves away from a point source

Energy/intensity is proportional to 1/d2* (d = distance)

At 1 unit distance = 1/1 2* = 1

At 2 units distance = 1/2 2* =1/4

At 3 units distance = 1/3 2* =1/9

Note: 2* denotes squared

Front 34

Effect of Distance - Doubling Distance

Back 34

Doubling of distance means a reduction of noise of 6 dB

Front 35

Controlling Noise - General Principles

Back 35

Eliminate at source, or control so far as is reasonably practicable at source (e.g. by relocation, redesign and maintenance)

Control along the transmission path (e.g. by using isolation, barriers and enclosures)

Control exposure at the receiver (e.g. by enclosures, acoustic havens, hearing protection zones and PPE, limiting exposure time, audiometry)

Front 36

Controlling Noise - Methods (1)

Back 36

Engineering controls

Selection of equipment (presses instead of hammers)

Location of pipe-work and ducting

Reduce operation speeds

Distance/orientation

Maintenance (balancing, sharpening, tightening)

Front 37

Controlling Noise - Methods (2)

Back 37

Enclosure (noise enclosures)

Isolation (noise havens, springs to absorb energy)

Silencers (air movements/absorptive reactive)

Lagging

Damping (pads, stiffening)

Screens

Absorption

PPE

Front 38

Acoustic Enclosure - Design (1)

Back 38

Keeps noise in

Heavy outer wall (plasterboard and brickwork)

Inner lining of acoustically absorbent material

Absorbent covered in protective mesh

Flexible pipes to form vibration breaks

Services in through ground

Inspection door double/triple glazed

Access panels for maintenance

Front 39

Acoustic Enclosure - Design (2)

Back 39

Access doors airtight

Any joints to outside sealed

Motors on dampers

Machines covered in enclosures

Avoid contact between equipment and walls

Sound absorbent material on floors

Silencers on any ventilation exits

Self-closing doors

Exterior controls

Front 40

Acoustic Haven

Back 40

Keep noise out

Air conditioned/lighting/thermal comfort/workstations

Viewing windows

Emergency response (fire alarms etc)

Above workplace for better view

External surface reflective

Internal acoustic absorbent

Internal walls cleanable

Isolated from floor and ceiling

Double/triple glazed

Air supply through lagged pipework

Front 41

Hearing Protection - Basics Principles (1)

Back 41

Selection is critical

Matched to noise characteristics

Will only be effective when used

Types and specifications:

Ear defenders

Semi-inserts

Earplugs

Active hearing protection

Front 42

Hearing Protection - Basics Principles (2)

Back 42

Mean attenuation values atfrequency bands 63-8000 Hz

Subjective test - 16 test subjects

Standard deviation values for each (+/- 84%)

Assumed protection values at each frequency ( = mean – one standard deviation)

HML (high, medium, low) values

SNR (single number rating)

Front 43

Hearing Protection - Selection

Back 43

Use HML (apply formula)

Use SNR

Octave band frequency

Front 44

Hearing Protection - Single Number Rating (SNR)

Back 44

Simple guide to hearing protection required:

Noise Level dB(A) & SNR Required

85-90 - 20 or less

90-95 - 20-30

95-100 - 25-35

100-105 - 30 or more

Front 45

Vibration - Basic Principles

Back 45

Oscillating movement of a fixed point due to applied energy

Front 46

Vibration - Basic Terms

Back 46

Displacement (amplitude) – maximum distance moved from the point of oscillation

Frequency – number of complete oscillations per second (Hertz)

Velocity – speed of the oscillating object at a fixed point in time (m/s)

Acceleration – maximum rate of increase in speed (m/s2 )

Magnitude – Vibration at Work Regulations 2005 = acceleration

Front 47

Measurement of Vibration

Back 47

Accelerometer

Average (root-mean-square) of acceleration in three planes

Weighting given to most harmful frequencies (8-20 Hz)

Expressed as A(8)- daily exposure

Front 48

Hand Arm Vibration Syndrome (HAVS)

Back 48

Impaired circulation to fingers - blanching (white finger)

Numbness in fingers, reduced sensitivity, tingling

Loss of dexterity

Loss of grip strength

Pain (especially in cold weather)

Infection/gangrene

Carpal Tunnel Syndrome and associated symptoms

Front 49

Whole Body Vibration

Back 49

Range of health effects

Back pain

Nausea

Gastrointestinal upsets

General feeling of discomfort, includingheadaches

Loss of equilibrium (balance)

Abdominal pain

Front 50

Factors Contributing to Risk

Back 50

Damage depends on:

Vibration magnitude

Vibration frequency

Duration of exposure

Individual susceptibility (diabetics/smokers more at risk)

External temperature

Tightness of grip

Front 51

Control of Vibration at Work Regulations (CVWR) 2005 - EAVs & ELVs

Back 51

Exposure limit values and exposure action values:

Hand-arm vibration:

EAV 2.5 ms-2 A(8)

ELV 5.0 ms-2 A(8)

Whole body vibration:

EAV 0.5 ms-2 A(8)

ELV 1.15 ms-2 A(8)

A(8) vibration dose averaged over an 8-hour shift

Front 52

CVWR - ELV

Back 52

Must not be exceeded

If exceeded then:

Reduce exposure to vibration to below the limit value

Identify the reason for that limit being exceeded

Modify the measures taken to ensure it does not happen again

Front 53

CVWR - ELV

Back 53

Provide appropriate health surveillance (Regulation 7)

Provide adequate information, instruction and training (Regulation 8).

Front 54

CVWR - Risk Assessment

Back 54

Reg 5:

Risk assessment required if employees are exposed to risk due to vibration

Assessment to consider:

The frequency and magnitude of vibration

The health effects of exposure to vibration

Any information provided by the manufacturers of work equipment

The availability of replacement equipment designed to reduce exposure to vibration

Specific working conditions such as low temperatures appropriate information obtained from health surveillance

Front 55

Estimating Daily Exposure

Back 55

Graph

Points system

Front 56

Hand Arm Vibration - Controls

Back 56

Automation

Change of work method

Modify/use alternative equipment

Purchasing policy

Maintenance

Monitor exposure and enforce limits Job rotation

Instruction and training

Health surveillance

PPE - gloves to keep hands warm

Warm temperatures

Front 57

Hand Arm Vibration - Health Surveillance

Back 57

Tier 1 - A short questionnaire used for new workers

Tier 2 - A short questionnaire for employees already exposed

Tier 3 - This involves a HAVS health assessment by a qualified person, if the assessment shows that the employee has HAVS, Tier 4 will apply

Tier 4 - Formal diagnosis by occupational health physician

Tier 5 - Optional: referral for further tests

Front 58

Hand Arm Vibration - Tier 3/4 Assessment

Back 58

Grip strength

Muscular dexterity

Vascular

Finger rewarming after cold provocation

Finger systolic blood pressure

Sensorineural

Vibrotactile perception threshold

Thermal perception threshold

Front 59

Hand Arm Vibration - Stockholm Workshop Scales (Sensorineural)

Back 59

Stage - Description:

0SN - Vibration exposed & no symptoms

1SN - Intermittent numbness with or without tingling

2SN - Intermittent or persistent numbness, reduced sensory perception

3SN - Intermittent or persistent numbness, reduced tactile discrimination and/or manipulative dexterity

Front 60

Hand Arm Vibration - Stockholm Workshop Scales (Vascular)

Back 60

Stage - Grade - Description:

0 - No grade - No attacks

1V - Mild - Occasional attacks affecting tips of one or more fingers

2V - Moderate - Occasional attacks affecting distal and middle (rarely also proximal) phalanges of one or more fingers

3V - Severe - Frequent attacks affecting all phalanges of most fingers

4V - Very severe - As in stage 3 with trophic skin changes in the fingertips

Front 61

Whole Body Vibration - Controls

Back 61

As for HAVS e.g. maintenance/automation etc

Specific examples:

Drive vehicles more slowly

Ergonomic design of vehicle cabs

Mount seats on springs or compression pads/ provide cushions

Provide rubber mats for standing tasks