Block 4 - Unit 7: Noise Controls

Labeling Requirement For Areas & Equipment

-A Hazardous noise area with any exposure at or above 85 dBA shall be clearly identified by signs located at entrances to, or the borders of, the area & will include pathways leading to the hazardous noise area *Signs will have he following message -CAUTION -HAZARDOUS NOISE AREA -HEARING PROTECTION REQUIRED

Personal Protective Equipment as Applied to Receiver

-After considering all other options, personal protective equipment such as earplugs or muffs may be required -These will be discussed in detail in the following unit

Machine Treatments

-Aim to reduce equipment vibration, & thus the accompanying noise, can be done a number of ways -Simple maintenance is all that is needed in many cases -Malfunctioning or poorly maintained equipment makes noise than properly maintained equipment

AFI 48 - 127

-All personnel shall wear hearing protection in a hazardous noise sources are operating, regardless of exposure

Engineering Controls

-Are at the source or the path

Enclosures

-Are barriers that are wrapped around a machine -They may be partial enclosures that leave the top or one side open or total enclosures that cover the entire machine -Total Enclosures provide much more sound reduction, but cause heat build-up that may cause damage to the machine

Administrative Controls

-Are usually at the path or receiver, & personal protective equipment is at the receiver

Source

-Controlling noise at its source is often the most reliable & permanent solution & should be considered first.

Shields & Barriers

-Function by deflecting the flow of energy away from the worker. -Example acoustical shield, usually attached to a machine, is a solid piece of material placed between the worker & the noise source -Example: An acoustical barrier is a larger piece of material & normally free standing

Direct Path

-In this path sound is transmitted directly to ear from the source to the receiver -However, it does not necessarily have to travel in a straight line -It could be omnidirectional-in all directions- or by the path of least resistance

Reflected Path

-In this path sound waves rebound from surfaces -An Example is an Echo -The sound level measured at any point in the room is the sum of the sound radiated directly by the source plus all the reflected sound -It is important to know the source & path of the noise when recommending controls -As far as controlling sound hazards, engineering controls are the first in the hierarchy of controls

Reduce Surface Response

-Increasing the mass of the surface is one way to cut down vibration because materials with greater thickness or density vibrate much less. -A method of reducing response in thin, Resonant surfaces is to deaden them with damping materials like rubber or elastic compounds that absorb noise -If it is not feasible to control noise at the source the next best choice is at the path

Process Substitution

-Is an engineering controls that includes process elimination, process changes, and/or design changes. -Design changes include using different tools, workstations, or equipment -Substituting quieter methods is also effective & can be more economical than other engineering controls. -Make sure the substitution does not result in trading one hazards for another

Reduce the Driving Force

-Is the mechanical disturbance creating the vibration. -Rotational forces, such as those produced by motors, can be controlled by reducing speeds, replacing worn parts, balancing, alignment, or lubrication. -Sliding forces can be decreased with lubrication or other means of lessening friction -Impact forces can be reduced by many of the substitution methods discussed previously, such as less force over a longer period or exchanging components such as gears for quieter parts -If the noise is form turbulent flow of air or liquid, changes cam be made to reduce the obstacles in the path of the flow or make those obstacles more aerodynamic

Administrative Controls as Applied to Path & Receiver

-Job Rotation -Changes in production schedules -Time limitations decrease the duration of exposure. Dose is based on intensity & duration. So, limiting the amount of time an individual uses a machine or piece of equipment, will decrease their exposure or dose -Implement a "buy-quiet program". This program prevents potentially hazardous noise from entering the work area by purchasing quieter equipment -Schedule & ensure completion of preventive maintenance -Training -Labeling

Paths of Noise

-Noise travels in two paths: *Direct *Reflected

Room Treatments

-Reflected noise can be prevented by the use of acoustically absorbent materials that are applied directly to the wall or ceiling surface -Additionally, materials can be suspended can be suspended from the ceiling in the form of hanging baffles -Gaskets designed with noise attenuating capabilities can be used to seal doorways -Specific applications involving the type, amount configuration, & placement of sound absorbent materials need to be determined based on an engineering evaluation

Product Substitution

-The Air Force requires that new equipment being considered for purchase have the lowest sound emission levels that are technologically & economically feasible -Some manufactures even provide noise data, such as estimated sound intensity

Path

-The direct path of noise, the open space between the noise source and the worker, is the most obvious path in which to place controls, -However, the possibility of reflected noise from walls or other surfaces should not be forgotten

Hazardous noise sources will be labeled where possible within AFVA 48-103, 48-104, and/or 48-150

-To warn operators of the need to wear hearing protection -Workplace supervisors, in consultation with BE, will ensure each tool or piece of equipment producing noise levels greater than or equal to 85 dBA, including vehicles, shall be conspicuously marked, where feasible, to alert personnel of the potential hazard. -The exception a "hazardous noise," & the equipment is stationary

Isolate the Responding Surface

-When modification of the driving force is not practical, attempt to isolate the responding surfaces (the surface that the machine hits or slides across) -Metal machines guards & equipment casing are typical examples of isolation methods -Other situations may call for simple solutions as rubber washers or cushions placed around the responding surfaces

AF Visual Aid (AFVA) 48 - 101

-Wording such as "When machines are operating" or "Withing 25 ft of operating band saw" may be added at the bottom of the caution sign to accurately identify the noise hazard area. -Whenever such modifications are required, the BE will specify the exact wording to be used