1. Noise Control Practices
Dr. Wesam Al Madhoun
Today we will cover some simple principles to assist you in reducing noise exposures in the workplace 1

2. Before We Discuss Noise Control Let’s Review Some Noise Concepts
Noise Measurements
Noise Levels are Expressed as Decibels (dB)

3. DEVICE dBA Computer 37 - 45 Refrigerator 40 - 43 Cloths Dryer 56 – 58
Garbage Disposal
Vacuum Cleaner
Leaf Blower
Circular Saw
Typical Noise Levels of Everyday Household Appliances 3

4. 1+1+1 Does Not Equal to 3 “Shake and Roll”
The Decibel is a Logarithmic Unit of Measure So We Can’t Simply Add Numbers.
“Shake and Roll”
How We Perceive Noise

5. Most measuring devices are only accurate +/- 1 dB
Audiometric tests are based on 10 decibel increments 5

6. High Frequency Noise Power Tools, Saws, Grinders
Other High RPM Equipment
Sudden Release of Pressure
Are Created By things like
High Frequency Noises Deflect Easier, Are Easier to Shield, Are Easier to Insulate. 6

8. Low Frequency Noise Power Presses Pumps, Compressors
Other Low RPM Equipment
Low frequency noises are created by things like ……
Low frequency Noises Can Travel Around and Through Objects and Are Harder to Shield and Absorb 8

10. Harmful Effects of Noise Are Related to the Noise Dose
Is the Noise Harmful?
Ask Yourself:
How Loud, How Long, How Many Times?

11. Noise Dose is a Combination
Intensity of Noise (how loud)
Duration of Noise Exposure (how long)
Frequency (how many times during the day are they exposed to such a noise)
It’s a combination of all three 11

12. Noise
Regulated as an 8 hour Time Weighted Average (TWA)
An 8 hr TWA of 90 dBA is designated as a Noise Dose of 100%

13. First Rule of Thumb 5 dB Halving Rule
For Each 5 dB Increase in Noise, In order to be Equivalent to the Previous Dose You Must Half the Allowable Exposure Time 13

14. Equivalent Dose of 90 dBA Over an 8 Hour TWA Period
95 dBA over 4 Hour TWA Period
100 dBA over 2 Hour TWA Period
105 dBA over 1 Hour TWA Period
110 dBA over ½ Hour TWA Period
For example, these exposures are all equivalent to a dose received from a 8 hour exposure at 90 dBA 14

15. Duration (How Long)
The 5 dB Rule Can Be Useful in Estimating Whether a Noise or an Activity Would Result in Employees Being Exposed to Noise In Excess of the PEL

16. Example
An Employee Must Enter a Pump Room and Conduct Preventative Maintenance
The Small Portable Sound Level Meter Reads 105 dBA Inside the Pump Room
How Long Could the Employee Stay in the Pump Room Without Exceeding the Dose Equivalent Noise Exposure of 90 dBA over an 8 hour TWA?

17. Administrative Controls
Answer
Employee Noise Exposure for 1 Hour at 105 dBA Would Be the Dose Equivalent Exposure of 90 dBA for an 8 Hr TWA
Administrative Controls
Likewise, Limiting Employee Exposure Time to Noise Can Help Reduce the Possibility of Hearing Loss

18. Watch Where You’re Standing
Employee Noise Exposures Often Depend on How Close They Are to the Noise Source
Distance
Noise Quickly Decreases as You Move Away from the Noise Source

19. 6 dB Double Distance Rule
Noise Will Decrease 6 dB Each Time You Double the Distance (free field, point source only)
See notes on slide #29 19

21. 6 dB Rule Would Not Apply
This only applies to a point source. If for example you were in a enclosed area like in a small factory or pump room, sound waves would deflect off walls and add to the total room noise. “The whole room seems to be filled with noise”
Noise would decrease away from the source but because of so many other factors it would not necessarily follow 6 dB Distance Rule. 21

22. 6 dB Rule Would Not Apply
Same thing 22

23. Distance From the Noise Source
Is It Possible to Move the Employee Workstation or the Noise Source?
With this in mind is it possible to …
Moving the Employee or the Noise Source Doesn’t Eliminate the Loud Noise, it Just Reduces the Employee Exposure to it! 23

24. In Moving the Source, Have You Created a Problem for Someone Else?
Think Out Loud
In Moving the Source, Have You Created a Problem for Someone Else?
Isolation Methods
Can You Isolate the Noise Source or The Employee From the Noise Source?

25. Enclosing the Employee
The Cab of Heavy Earth Moving Equipment is a Good Example. They are Insulated (and Air Conditioned).

26. Isolation Methods
Install Barriers Between the Employee and Noise Source
Enclose the Noise Source
Enclose the Employee

27. Think Out Loud Be Careful When Constructing Barriers or Enclosures.
Noise May be Deflected Backwards Off the Barriers or the Walls of the Enclosure Which Can Increase the Noise Intensity on the Noise Source Side.
Employees who Must Service Equipment or Conduct Work in Those Areas May Now be Exposed to Greater Noise than Before

28. Deflection of Sound Waves in Enclosure Creates Louder Noise
Unless You add absorbing materials on the walls, ceiling, or floor
Which brings us to our next subject 28

29. Noise Absorbing Material
The Good
Noise is Absorbed, It’s Gone, It Wouldn’t Bother Anyone Anymore
High Frequency Noises are Easier to Absorb

30. The Bad Some Types Can be Fragile Some Types Can be Hard to Clean
Some Can Be Expensive
Some types of absorbing materials can be ………… 30

31. The Ugly Some Types Can Be Very Expensive
Some Types Won’t Hold Up to Chemicals or Moisture
Some Types Can be Combustible
Oil and hydraulics fluids can damage absorbing materials
Water can ruin materials or produce perfect environment for mold and mildew 31

32. Consideration of materials used
Climate
Ease of installation
Durability - resistance to degradation from compression, moisture, decomposition, etc.
Ease of replacement at end of life
Cost effectiveness
Toxicity
Flammability
Environmental impact and sustainability

33. Glass
Brick

34. Hardwood

35. Softwood

36. Fiberglass rigid panel

37. Polystyrene
Cementitious foam
Air-entrained concrete

40. Transmitting Vibration
Noise and Vibration Can Be Transmitted to Other Surfaces Which Then also Transmits Noise

42. Controlling Noise Generated by Vibration Sources
Springs, or Isolation Material under Motors and Large Equipment
Ensure Plates, Covers, Doors, and Access Panels are Securely Attached
Bent or Warped Shafts on Motors and Fans Can Create Vibration
Bad Bearings, Flywheels, Pulleys, Fan Blades, and Belts
If a piece of machinery is causing the concrete to vibrate under your feet what do you think it’s doing to the integrity of the foundation, sooner than later it’s going to fatigue and crack!
Loose screws!
Poor Maintenance! 42

44. By the Way
Poor Maintenance Can Be a Major Source of Noise Exposure and One Which is Often Consider Economically Feasible.

45. Controlling Noise Created By Released Air
Muffler systems on Pneumatic Equipment When Available
Reduce Air Pressure if Possible
Discourage the Use of Compressed Air for Cleaning Purposes

46. You May Not Be The First Person To Ask
Contact the Manufacturer of the Equipment and Request Assistance in Determining Ways to Help Decrease Noise Output of the Machines
Finally 46

47. Hearing Protection is not a Noise Control Method
Hearing Protection does not Reduce Employee Noise Exposure,
It Reduces the Potential Harm Which Could Otherwise Result in an Unprotected Employee

48. Like Respirators, They are Only Effective if Used Properly
Hearing Protectors
Like Respirators, They are Only Effective if Used Properly
Ear Plugs and Other Types of Hearing Protection Have Limitations on How Much Protection They Can Provide

49. Noise Management Strategy

50. The techniques employed for noise control can be broadly classified as:
Control at source
Control in the transmission path
Using protective equipment.

51. Noise Control at Source
Reducing the noise levels from domestic sectors:
The domestic noise coming from radio, tape recorders, television sets, mixers, washing machines, cooking operations can be minimized by their selective and judicious operation.
By usage of carpets or any absorbing material, the noise generated from felling of items in house can be minimized.

52. Maintenance of automobiles:
Regular servicing and tuning of vehicles will reduce the noise levels.
Fixing of silencers to automobiles, two wheelers etc., will reduce the noise levels.
Control over vibrations:
The vibrations of materials may be controlled using proper foundations, rubber padding etc. to reduce the noise levels caused by vibrations.
Low voice speaking: Speaking at low voices enough for communication reduces the excess noise levels.

53. Prohibition on usage of loud speakers:
By not permitting the usage of loudspeakers in the habitant zones except for important meetings / functions.
Selection of machinery:
Optimum selection of machinery tools or equipment reduces excess noise levels.
Maintenance of machines:
Proper lubrication and maintenance of machines, vehicles etc. will reduce noise levels.
For example, it is a common experience that, many parts of a vehicle will become loose while on a rugged path of journey.

54. Control in the transmission path
If these loose parts are not properly fitted, they will generate noise and cause annoyance to the driver/passenger.
Similarly is the case of machines. Proper handling and regular maintenance is essential not only for noise control but also to improve the life of machine.
Control in the transmission path
The change in the transmission path will increase the length of travel for the wave and get absorbed/refracted/radiated in the surrounding environment.

55. Installation of barriers:
Installation of barriers between noise source and receiver can attenuate the noise levels.
For a barrier to be effective, its lateral width should extend beyond the line-of-sight at least as much as the height.
The barrier may be either close to the source or receiver, subject to the condition that, R <<D or in other words, to increase the traverse length for the sound wave.
It should also be noted that, the presence of the barrier itself can reflect sound back towards the source.

56. At very large distances, the barrier becomes less effective because of the possibility of refractive atmospheric effects.

57. Design of building:
The design of the building incorporating the use of suitable noise absorbing material for wall/door/window/ceiling will reduce the noise levels.
The approximate reduction of outside noise levels using typical exterior wall construction is given at Table 6.
Green belt development:
The degree of attenuation varies with species of greenbelt.
The typical attenuation of noise levels by trees is presented at Fig. 7 (a) and (b).
The statutory regulations direct the industry to develop greenbelt four times the built-up area for attenuation of various atmospheric pollutants, including noise.

60. Using protection equipment
Protective equipment usage is the ultimate step in noise control technology, i.e. after noise reduction at source
and/or after the diversion or engineered control of transmission path of noise.
The first step in the technique of using protective equipment is to gauge the intensity of the problem, identification of the sufferer and his exposure to the noise levels.
The usage of protective equipment and the worker's exposure to the high noise levels can be minimized by -:
Job rotation: By rotating the job between the workers working at a particular noise source or isolating a person, the adverse impacts can be reduced.

61. Exposure reduction: Regulations prescribe that, noise level of 90 dB (A) for more than 8 hr continuous exposure is prohibited.
Persons who are working under such conditions will be exposed to occupational health hazards.
The schedule of the workers should be planned in such a way that, they should not be over exposed to the high noise levels.
Hearing protection: Equipment like earmuffs, ear plugs etc. are the commonly used devices for hearing protection.
Attenuation provided by ear-muffs vary widely in respect to their size, shape, seal material etc.
Literature survey shows that, an average noise attenuation up to 32 dB can be achieved using earmuffs.

62. Traffic Control Measures
Reducing road traffic noise at source:
imposing permissible noise emission limits;
(b) promoting the use of public transport; and
(c) cracking down illegal vehicle modifications such as muffler alterations
Land use planning:
zoning land and planning urban projects with the consideration of the noise factor;
(b) building bypasses and ring roads; and
(c) establishing buffer zones on each side of a road.

63. Resurfacing roads with low-noise materials:
Resurfacing roads with low-noise materials to reduce noise from tire friction.
Generally speaking, low-noise pavement can attain a reduction of noise from 3 dB(A) to 5 dB(A).
Installing double-glazed windows and air-conditioning for the affected residents
Adopting advanced construction methods
employing a jointless construction method for elevated roads and bridges; and
installing sound-absorbing panels on the underside of elevated roads.

64. Prohibition of certain vehicle types (usually trucks) from a particular route or restricting vehicles from operating during noise sensitive times of the day.
The prohibition of trucks from a major roadway can produce up to an 8 to 10 dB reduction in noise, at times providing an adequate traffic management abatement measure.