Noise Control Practices - Islamic University of Gaza

Noise Control Practices - Islamic University of Gaza

Noise Control Practices Dr. Wesam Al Madhoun Noise Before We Discuss Noise Control Lets Review Some Noise Concepts Noise Measurements Noise Levels are Expressed as Decibels (dB)

DEVICE dBA Computer 45 - 37 Refrigerator

43 - 40 Cloths Dryer 58 56 Garbage Disposal 83 - 76

Vacuum Cleaner 89 - 84 Leaf Blower 105 - 95 Circular Saw 104 - 100

1+1+1 Does Not Equal to 3 The Decibel is a Logarithmic Unit of Measure So We Cant Simply Add Numbers. Shake and Roll How We Perceive Noise

High Frequency Noise Power Tools, Saws, Grinders Other High RPM Equipment

Sudden Release of Pressure High Frequency Noises Deflect Easier, Are Easier to Shield, Are Easier to Insulate. Low Frequency Noise Power Presses

Pumps, Compressors Other Low RPM Equipment

Low frequency Noises Can Travel Around and Through Objects and Are Harder to Shield and Absorb Harmful Effects Harmful Effects of Noise Are Related to the Noise Dose Is the Noise Harmful?

Ask Yourself: How Loud, How Long, How Many Times? 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) 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% 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 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 Hour TWA Period 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 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? 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 Watch Where Youre 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

6 dB Double Distance Rule Noise Will Decrease 6 dB Each Time You Double the Distance source only)

(free field, point dB Rule Would Not Apply 6 dB Rule Would Not Apply 6 Distance From the Noise Source Is It Possible to Move the Employee Workstation or the Noise Source?

Moving the Employee or the Noise Source Doesnt Eliminate the Loud Noise, it Just Reduces the Employee Exposure to it! 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? Enclosing the Employee The Cab of Heavy Earth Moving Equipment

is a Good Example. They are Insulated (and Air Conditioned). Isolation Methods Install Barriers Between the Employee and Noise Source

Enclose the Noise Source Enclose the Employee 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

Deflection of Sound Waves in Enclosure Creates Louder Noise Noise Absorbing Material The Good Noise is Absorbed, Its Gone, It Wouldnt Bother Anyone Anymore

High Frequency Absorb Noises are Easier to

The Bad Some Types Can be Fragile Some Types Can be Hard to Clean

Some Can Be Expensive The Ugly Some Types Can Be Very Expensive Some Types Wont Hold Up to Chemicals or

Moisture Some Types Can be Combustible Consideration of materials used Climate Ease of installation Durability

- resistance to degradation compression, moisture, decomposition, etc. Ease of replacement at end of life

Cost effectiveness Toxicity Flammability Environmental impact and sustainability from Glass Brick

Hardwood Softwood Fiberglass rigid panel Cementitious foam Air-entrained concrete Polystyrene

Transmitting Vibration Noise and Vibration Can

Be Transmitted to Other Surfaces Which Then also Transmits Noise 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 By the Way Poor Maintenance Can Be a Major

Source of Noise Exposure and One Which is Often Consider Economically Feasible. 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 You May Not Be The First Person To Ask

Contact the Manufacturer of the Equipment and Request Assistance in Determining Decrease

Machines Noise Ways Output to of Help

the Hearing Protection Hearing Protection is not a Noise Control Method Hearing Protection does Employee Noise Exposure,

not Reduce It Reduces the Potential Harm Which Could Otherwise Result in an Unprotected Employee 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 Noise Management Strategy

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

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. 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 <

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 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 -: 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. Traffic Control Measures Reducing road traffic noise at source:

(a)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: (a)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.

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. 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.

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