Source control begins with a thorough analysis of each piece of noise-generating equipment. You should attempt to identify all noise sources within a given piece of equipment, as well as the ways in which the sound is transmitted (and often amplified via resonance or vibration) to the surrounding room. Then every effort should be made to both quiet the sources and dampen the resonant path-ways of transmission. Noise sources generally include motors, gears, belts and pulleys, points of operation where blades touch wood, and any other moving parts. Resonant transmitters generally include the frames, footings, and housings of the equipment.

Possible Solutions

• Maintaining motors and all moving parts in top operating condition. Maintenance involves lubricating and cleaning; replacing worn parts; maintaining proper belt tensions and bolt torques; and properly balancing pulleys, blades, and other rotating parts.

• Reducing the speed of operation of the equipment to the slowest level consistent with product quantity and quality goals.

• Moving power equipment operations out of wooden or steel-frame buildings and into stone, cement, or brick structures, if at all possible.

• Ensuring that equipment frames are as rigid as possible, that equipment is firmly seated on a solid floor (preferably cement slab), and that no piece of equipment is in contact with any other piece or with walls.

• Isolating noisy equipment with rubber footings, springs, or other forms of damping suspension so as to reduce the radiation and amplification of noise via vibrations.

• Applying vibration-damping materials to all resonating surfaces, and constructing (where possible) sound absorbent hoods around points of operation.

Effective path controls involve isolating, blocking, diverting, absorbing, or otherwise reducing noise intensity before it reaches your employees' ears.

Possible Solutions

• Segregating operations so as to limit, as far as possible, the number of employees exposed to excessive equipment noise.

• Enclosing equipment within barriers de-signed to absorb noise and/or reflect it in harmless directions, such as toward ceilings covered with sound absorbent material.

• Moving or locating noise-producing equipment away from employees, since noise intensity decreases significantly as you move away from the source of the noise. Depending on the types of surfaces in your workplace, you can reduce the level of noise that your workers are exposed to by up to 6 dBA by doubling the distance between the source of the noise and your workers. The presence of reflective surfaces (such as flat metal surfaces) in the workplace will reduce the level of noise reduction achieved by this method.

Hearing protection devices isolate the human ear from harmful noises. They should be worn by employees as the final line of defense against noise hazards. Hearing protection devices can be effective and, compared to source and path control efforts, relatively inexpensive. Their use, however, does demand a considerable level of ongoing effort and commitment.

• Given the nature of woodworking operations, production floor employees will almost certainly require hearing protection devices.