Physical Work Environment: Acoustics, health and safety hazards, measurements and standardization, Control Procedures

1. Dr. Sanjib Kumar Das, PhD
Noise

2. What is Sound?
• Sound consist of mechanical oscillations in a
medium.
• The sound is audible for frequencies between 20
Hz to 20,000 Hz.
• Sound propagates in waves.
• Air propagation is termed as “Air-borne sound”
and propagation in solid bodies is termed
“structure-borne sound”.

3. Sound Depends On:
 A vibrating source
to set up the sound
waves
 A medium to carry
the waves
 A receiver to
detect them

4. Which Would Be the Best
Conductor?
 Solid?
 Liquid?
 Gas?
 Solid – The
Bricks!

5. Sound Travels at Different Speeds Through
Different Media
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
20,000
AIR WATER GRANITE
 Feet per second

6. What is noise?
 Unwanted sound.
 When unwanted noise gets loud enough
– It is unpleasant
– It is distracting
– It is tiring & stressful
– Higher levels may cause permanent hearing
damage

7. Noise is an ancient problem!
 Roman poets
complained about the
racket of iron cart-
wheels on the cobbles

9. Prologue…..
 In the UK there are
over 170,000 people
with significant
work-related hearing
damage
 14,200 are serious
enough affected to
receive disablement
benefit

10. NOISE STATISTICS
High Risk workers and Industries
- Highest Risk workers are (88% of all claims):
- Laborers
- Machine operators
- Transport workers
- High risk Industries:
- Manufacturing
- Construction
- Electricity, water supply
- Mining
- Transport

11. Effect of noise on Human

12. Damage can include:
 Temporary hearing loss
– hearing returns after a
short period away from
noise
 Permanent hearing loss
– Permanent damage or
destruction of hair cells in
the ears.
– Hearing cannot be
restored

13. Signs of developing hearing loss
 Inability to hear soft or high pitched
sounds
 Trouble understanding conversation at
a distance or in a crowd
 Ringing in the ears
 Others can hear something you can’t

14. DO YOU HAVE A NOISE PROBLEM?YOU DO IF:
1. You have to raise your voice when talking to someone about
one meter away
2.Workers say their hearing sounds are dull at the end of the
shift.
3. Workers experience ringing in their ears during or after work.
4. If any of these symptoms are present the noise will be around
85dB(A) or greater!! And risk assessment should be conducted.

15. Effects of Noise Exposure
• The damage from exposure to noise
occurs in the inner ear.
• There are tiny hair cells in this part of
the ear that are flattened out when
exposed to noise.
• If the exposure is short, the hair cells
raise back up. If the exposure is long
or extremely loud, the hair cells don’t
recover and hearing ability is reduced.
• When all the hair cells are damaged,
complete deafness occurs.
• “People who say they are “used to the
noise” often have already lost some of
their hearing.”
Damage occurs in this part of
the ear

16. EFFECT OF LOUD NOISE ON HEARING
hair cells in the Cochlea
Healthy hair cells Serious Hearing loss
The cilia (
sensory hairs)
appear normal
Loss of cilia as
a result of
Noise

17. There is no cure for hearing damage!
 Normal hearing can
never be restored
 Hearing aids do not
restore noise-damaged
hearing
 At best, they help the
person a little

18. Exposure to noise may pose a variety of
health and safety risks to workers

19. Hearing loss:
Excessive noise damages the hair cells in the cochlea, part of the inner
ear, leading to loss of hearing. ‘In many countries, noise-induced hearing
loss is the most prevalent irreversible industrial disease.’ It is estimated
that the number of people in Europe with hearing difficulties is more
than the population of France.
Loud noise can cause:
Acoustic Trauma
-immediate damage from unprotected exposure to very intense or explosive
sounds (e.g. gunshot, explosion, nail guns)
Temporary Threshold Shift
may last hours or longer depending on the degree of noise exposure.

20. Permanent Threshold Shift
• Severe noise exposure is repeated over many years.
• Problems communicating.
• Reduced ability to hear high pitched sounds, eg. S, T, H,
K, F, C, consonants.
• Accused of ‘selective deafness’
Tinnitus
• Ringing in the ears

21.  Physiological effects:
There is evidence that exposure to noise has an effect on the
cardiovascular system resulting in the release of catecholamines and
an increase in blood pressure. Levels of catecholamines in blood
(including epinephrine (adrenaline)) are associated with stress.
 Work-related stress:
Work-related stress rarely has a single cause, and usually arises from
an interaction of several risk factors. Noise in the work environment
can be a stressor, even at quite low levels.
 Increased risk of accidents:
High noise levels make it difficult for staff to hear and
communicate, increasing the probability of accidents. Work-related
stress (in which noise may be a factor) can compound this problem.

22. Noise exposure and pregnancy
Recent review of the literature (American
Academy of Pediatrics, 1997) concludes that:
Exposure to noise during pregnancy may result in
high-frequency hearing loss and may be associated
with premature birth and foetal growth retardation.

23. OTHER HEALTH EFFECTS
These health effects may occur at exposures LESS than Standard -
includes:
Annoyance
-interferes with conversation, concentration,
-disturbs judgment
-increases anxiety
Task distraction
Clinical health effects
-raised blood pressure, increased heart rate, heart disease and stress
-reduced white blood cell counts
-reduced immune response

24. Non-Auditory Effects of Noise
 Job dissatisfaction
 Somatic complaints (e.g. headaches)
 Anxiety
 Post work irritability
– Impatience
– Nervousness
– Generally inability to unwind

25. Non-Auditory Effects Of Noise
 Physiological
– Stress Arousal
– Sleep Disturbance
 Psychological
– Annoyance
– Behavioral
 Communication
 Cognition

26. Physiological Stress
 Noise is biological stressor
Activated at 65-70dBA
 What is it?
– Body’s reaction to any stressor requires an adjustment or
response
 The reaction to stress can be physical, mental or emotional
 Causes of stress can come from your body, your thoughts,
or the environment
 Whatever the cause of stress, real or imagined, the body’s
response is real

27. Physiological: Sleep Disturbance
 60dB(A) Awakening
 Sleep disturbance is influenced by
– Characteristics of the noise
– Individual differences
– Age

28. Psychological Annoyance
 Annoyance
– A response to noise rather than an auditory perception of
it
 Closing a window when noise outside is too loud
 Noise is more likely to be annoying if
– Random
– Higher pitched
– Combined with warmer climate
– Occurs at night
 Threshold of annoyance
– 50-55dB(A)

29. Psychological Annoyance
 Annoyance is subjective
– Noise is likely to be an annoyance if one
perceives:
 Not necessary
 People causing the noise do not care about its
effects on those exposed to it
 The noise is not important to the economic and
social success of the community

30. Cognition
 Functions most affected
– Reading comprehension
– Attention span
– Problem solving
– Memorization
– Job performance

31. Communication
 Above 55-60dB(A) background noise interferes
with communication
 Armor Crew Performance (Garinther & Peters,
1990)
– Mission time completion increased from 40-90 seconds
– Crew killed by enemy increased from 7% to 28%
– Targets correctly identified decreased from 98% to
68%

32.  The blast is the pressure above the ambient air
pressure.
 The biological effect of the blast wave depends
on the peak overpressure and the positive phase
duration.
 Peak levels above 190 dBP is the point where
there are concerns about blast injuries.
Blast Injuries

33. Noise
– The “auditory” component
– Target Organ(s): inner ear
– Outcome: temporary to permanent hearing loss
Blast Injuries
Blast Overpressure
– The “non-auditory” component
– Target Organ(s): gas-containing organs (lungs*,
trachea, GI tract)
– Outcome: performance problems, mild to severe
hemorrhage

34. Non-Auditory Injuries
 Healthy
 Damaged

35. Noise Effects
 Steady State Noise
– 120 dBA Discomfort
– 140 dBA Pain
– 160 dBA Ear drum rupture
 Impulse
– 185 dBP Ear drum rupture
– 200 dBP Lung rupture & embolism

36. Measurement of Noise

37. Sound Level Meter
- Sound level meter is used for acoustic measurements. It is
commonly a hand-held instrument with a microphone. The
diaphragm of the microphone responds to changes in air pressure
caused by sound waves. Thus it is also referred as a sound
pressure level meter.
- Noise dosimeter is a specialized SLM intended to measure the
noise exposure of a person integrated over a period of time;
usually to comply with Health and Safety Regulations. Eg: The
noise dosimeter is worn by a miner as he goes about his daily
work.
- A frequency analysis is performed by specialist departments
using octave band filters.

38. Measurement of Noise Loudness (dB)
170 dB Jet airliner
120 dB Riveting hammer
110 dB Shouting loudly
70 dB Street sounds
38 dB Quiet bedroom
This is a logarithmic scale – an increase of 1dB
means about 30% more noise

39. Speed of Propagation
This standard gives three differing response speeds of the
sound level meter depending on the characteristic of
noise:
“Slow”-
For steady state noises that change only slowly and for
sound power measurements. The test values are indicated
by dB (AS).
“Fast”-
For noises which change rapidly and which last for longer
than 200 ms. The test values are indicated by dB (AF).
“Impulse”-
For impulse-type and short-period noises (from 1 ms to 200
ms). The test values are indicated by db (AI)

40. US Standards:
OSHA (Occupational Safety and Health
Administration, US Department of Labor)
OCCUPATIONAL NOISE EXPOSURE STANDARD:
- Effective from 7 October 2004
- Exposure standard must not be interpreted as a “NO
EFFECT” level
the standard of 85 dB (A) is considered to be an
“acceptable risk" for the working population.
e.g.. Exposure of 85 dB (A) for 8-hours a day over a
40-year period, 85% of male population can expect to
have an average of 10% hearing loss.

41. Comparison of regulations:
Health and Safety at Work etc. Act 1974 (Great Britain)
Noise at Work
Regulations 1989
Control of Noise at
Work Regulations
2005
Action
Upper
action
value
90 dB(A) 85 dB(A) Noise reduction at source
Ear Protection must be used
Lower
action
value
85 dB(A) 80 dB(A) Make Ear Protection
available
Maintenance programme
Training
Limit
value
- 87 dB(A) Reduce to below this level
Allowed to take hearing
protection into account

42. Indian Standards
Ministry of Environment and Forests : Noise Pollution (Regulation
and Control) Rules, 2000 under the Environment (Protection) Act
1986
Area Code Category of
Area/Zone
Limits in dB (A)
Day Night (10pm-6am)
A Industrial Area 75 70
B Commercial Area 65 55
C Residential Area 55 45
D Silence Zone 50 40

43. Daily Allowable Exposure Times to Noise
 The table below shows noise levels and how long a
person can be exposed without hearing protection before
there is damage to the ear.
 Noise Level Allowable Exposure Time
 85 decibels 8 hours
 90 decibels 4 hours
 100 decibels 1 hour
 105 decibels 30 minutes
 110 decibels 15 minutes
 115 decibels 0 minutes

44. Table for determination of test period
Sound Level Characteristics Test Period
Almost constant Approx. 20 seconds
Slight irregularities
(fluctuation<5 dB (A))
About 1 to 2 minutes
Pronounced irregularities
(fluctuation up to about 15 dB (A))
Up to about 10 minutes
Unforeseeable fluctuations
(fluctuation>15 dB (A))
Use recording device
over the assessment
period
Periodic For one period
e.g. for one machine cycle

45. Measuring and averaging the
noise levels at the workplace
• Assessment of workplace noise and for comparisons with
established standards are required.
• Sound sources to be recorded with mentioning details of
location, time, test period, instruments and their settings.
• When taking measurements, the microphone shall be
setup in such a way that noise typical of the work place
in the vicinity of the employee's ear is picked up.

46. principles of noise
reduction

47. Principles of noise reduction
CONSULTATION
TRAINING
INFORMATION
1. Identify Hazard
2. Assess risk
3. Control risk
4. Review

48. ASSESS THE RISK
May involve noise measurements:
 Sound level meter
Noise dosimeters
• Worn by worker –records personal noise
exposure

49. CONTROL PRINCIPLES
•Control at Source
•Control of transmission path
•Control at the receiver

50. CONTROL OF NOISE
HIERARCHY OF CONTROLS
- Eliminate
- Substitute (eg.“Buy quiet”/ design considerations)
- Engineering controls
- Administrative controls (eg job rotation)
- Personal protection
(does not reduce the noise hazard)
Combination of the above options is usually required
permanent
noise
reduction to
non-excessive
levels

51. CONTROLAT SOURCE
Eliminate activity/process creating noise
Eliminate hard surface to hard surface contact
in processes (eg metal to concrete)
Substitute activity creating noise
Purchase quieter equipment
•Electric forklifts instead of diesel/gas
Change to quieter processes
•Screws instead of nailing
Change operating conditions
•Reduce air velocity on fans
 Maintenance

52. Maintenance
•Worn
•Loose
•Lubricate
Purchasing policy
•Quieter process
•Buy low noise machines

53. The flow of fluid in the pipe causes vibration which may
be heard in the room and may be transmitted through the
structure of the building
Solution:
A flexible coupling in the pipe prevents vibration after the
coupling and this eliminates or reduces vibrations traveling
through the pipe and therefore reduces structure borne
noise
NOISE CONTROL EXAMPLES

54. Noise is produced on the side
handle of a compressed air
grinder
Solution: Develop a new handle
with porous
sound absorbent material
between fine meshed gauzes.
The turbulence is broken up by
the passage of air
and reduces the amount of
disturbed air.
NOISE CONTROL
EXAMPLES

55. NOISE CONTROL EXAMPLES
Instead of using a hammer to bend a piece of metal, a pair of
pliers can be used to avoid noise altogether.

56. In terms of sound intensity the 4” angle grinder is 4 times
quieter than the 9” angle grinder!!
The 9” angle grinder 108dB(A) The 4” angle grinder,102dB(A)
NOISE CONTROL EXAMPLES

57. CONTROL TRANSMISSION OF NOISE
Isolate sound using anti-vibration mountings
Increase distance from source to receiver
(Note: if distance from source is doubled, SPL
decreases by 6 dB)
Use sound absorbing surfaces
Enclose sound sources
Enclose person in soundproof cabin

58. Does this look
familiar?
This is how it should be
NOISE CONTROL EXAMPLES
TREATMENT OF NOISE PATH

59. NOISE CONTROL EXAMPLES
TREATMENT OF NOISE RECEIVER
- Where the noise levels cannot be (adequately) reduced at
the source, eg because of the nature of the machines or
equipment, or the building structure.
Solution:
- A sound proof
room around the
machine or the
worker.

60. High frequency sound is transported
directly to the worker’s ears from a
high speed riveting machine hood
Solution:
A sound insulating hood is placed around
the machine with a small opening for work
pieces towards the bottom. Safety glass is
placed in the upper part of the hood side
facing the worker. The safety glass reflects
the sound back onto the sound absorbent
material of the hood.
NOISE CONTROL EXAMPLES

61. Engineering control
Methods
•Reduce impact and vibration
•Transmission and belt noise
•Silencing
•Damping
•Partial enclosure
Anti-vibration mounts

62. Noise barrier

63. Noise barrier
Damping

64. Noise enclosure
Enclosure
•Mass
•Damping/absorption

65. ADMINITRATIVE CONTROL
- Areas or equipment where excessive noise
occurs must be signposted or marked at
Workplace

66. Hearing Protection-
The employer must provide hearing protection for all
employees that have an eight hour time weighted
exposure of 85 dBA or above, who have any
continuous exposure at or above 115 dBA, or who
have an exposure to any impulse noise levels above
140 dB.
ADMINISTRATIVE CONTROL
Employer’s Responsibility
What the WISHA Rules Require
Washington Industrial Safety and Health Act

67.  The WISHA* noise regulations require that we
have at least 2 types of hearing protection to
choose from.
 There are three types of hearing protection – ear
muffs, earplugs and ear caps.
 Ear muffs and earplugs provide about equal
protection, ear caps somewhat less.
CONTROL AT THE RECEIVER
Types of Hearing Protection
earmuffs
earplugs ear capsReference: Washington Industrial Safety and Health Act

68. Noise
Source
Reduction of
sound generation
Reduction of
sound radiation
Work
room
Reduction of
sound propagation
Person Reduction of
sound perception
•Selection of procedure
•Design of procedure
•Design modifications
•Enclosure
•Structure and room noise
•Segregation
•Personal hearing protection
Noise reduction possibilities
SoundPropagation

69. Don’t take noise for granted!