Occupation Noise

Question 1

Define sound and noise

Answer 1

Sound

• objective - pressure fluctuations detected by human ear
• subjective: any sensation of sound

Noise is unwanted sound, unpleasant, undesired by the recipient

Question 2

What is the decibel halving rule

Answer 2

A 3 dB increase will double the sound pressure level.

Double the intensity means halve the time you can be exposures 
85. = 8 hours
88. = 4 hours
91. = 2 hours
94. = 1 hour
97 = 30mins
100 = 15mins

Question 3

2 conduction pathway

Answer 3

Air conduction
- transmission along acoustic pathway

Bone conduction

• direct stimulation of cochlea by vibration
• physical vibration or loud sounds
• some protection from helmet

Question 4

How does noise degrade performance and safety

Answer 4

Psychological impact stress and distraction
Degraded communication
Hearing loss, temporary or permanent
Fatigue
Increased workload

Fluctuation of HR, RR, BP
Increased anxiety
Decreased GI motility
Alter regional blood flow
Vertigo
Disorientation
Vomiting

Question 5

Describe temporary vs permanent hearing losing and the difference

Answer 5

Temporary threshold shift

• acute exposure
• Muffled hearing
• tinnitus
• Rapid recovery

Noise induced hearing loss

• continued exposure
• high tone loss
• usually bilateral
• Irreversible

Question 6

Factors affecting NIHL

Answer 6

individual susceptibility
Age
Nature of noise: continuous/intermittent/impact
Noise intensity
Duration
Protective devices used
Continual and correct use of PPE

Question 7

Way to improve communication

Answer 7

Noise - attenuating headsets
Noise- canceling microphones
Radio procedures
- phonetic alphabet
- standard phraseology

Question 8

Psychological effects of noise

Answer 8

More harmful

• intermittent noise
• impulsive noise
• high frequency noise
• relevant noise
• prolonged exposure

Less harmful

• continuous noise
• low frequency noise
• irrelevant noise
• short-term exposure

More vulnerable tasks
- continuous task, prolonged vigilance, multi-tasking, auditory tasks

Les vulnerable task
- intermittent task, simple repetitive task, non-auditory tasks, physical exercise

More vulnerable people - introverts
Less vulnerable people - extroverts

Question 9

Clinical assessment

Answer 9

Audiogram
- if average loss > 15dB at any frequency
- inform the employee
- check noise exposure history
- check suitability/condition/fitting/use f HPD
- re-issue HPD f required
- retest in 6 months
Duty of care consideration

Question 10

Types of hearing loss

Answer 10

Industrial hearing less
- peak at 4000Hz

Age related changes - Presbyacusis
- ???

Infection - conductive hearing loss

Question 11

What is equivalent noise level

Answer 11

The overall noise within a measurement time interval expressed as single numbers

Question 12

Permissible daily exposure duration

Answer 12

Maximum period for which a person can be exposed without exceeding the OH&S limit for occupational noise.

Doesn’t take into account exposure when not at work

Question 13

What is the safe level of noise

Answer 13

Australian standard
Continue noise 85dB over 8 hours
Peak noise 140dB
Only reduces risk to <5%

Question 14

Aviation noise levels

Answer 14

Commonly 120-130 dB

Therefore required protection of 45dB

Question 15

Sources of noise around Military aviation

Answer 15

Aerodynamic noise
Engine noise
Environmental conditioning systems
Avionics and avionics cooling
Weapon systems
Auditory warning systems
Communication

Question 16

Factors affecting noise

Answer 16

Aircraft type
Altitude speed - lower you fly the noise it is
Aircraft design
Ancillary systems
Aerodynamics
Avionics
Communication, audible warmings
Weapons
Accommodation
Proximity of ground personnel

Question 17

Protection from noise

Answer 17

Engineering of control

• elimination
• enclosure
• isolate

Administrative control

• work scheduling
• job rotation
• Quiet work practices
• restricted areas

Personal protection
- Hearing protection devices

Question 18

Hearing protection devices

Answer 18

Ear muffs
Ear plugs - standard, communication or custom moulded 
Ear caps
Electronic cancellation of noise
Covering head and ears - helmet
Single or in combination

Question 19

Active noise reduction

Answer 19

Reverses frequency?

Question 20

Considerations in selecting HPD

Answer 20

Compliance with AS 1270
Provides adequate attenuation by avoids over- protection
Communication requirements
Comfort and wear time
Compatibility with workplace
Combing HPDs if required medical factors

Question 21

Hearing protection areas and and protection required

Answer 21

Amber 85–100, impulse 140-150 - ear muff or plug

Red 100-115 impulse 150-160 - ear muff

Black 115-120. Impulse 160-166 - Earmuff +plug

Extreme >120 impulse >166 - Earmuff +plug + time

Question 22

Audiogram requirements

Answer 22

Amber, red, black - initial then annually, on request and at termination

Extreame - initial, six monthly, on request and at termination.

Question 23

Noise induced hearing loss
A. Usually improves over time
B. Is a conductive hearing loss
C. Is centred around the 4kHz frequency band
D. Is an uncommon cause for compensation claims

Answer 23

C. Is centred around the 4 kHz frequency band