Noise barriers and enclosures are engineering controls that can reduce noise exposure. They are designed to reflect or absorb noise or do both. Dense materials such as steel and concrete are used to reflect or block sound. Soft, porous, low-density materials such as foam and fiberglass are use to absorb sound.

Through the use of specially designed barriers and enclosures, noise levels and exposures can be reduced. However, sound pressure levels within these structures may still be above the OSHA permissible exposure limit and workers may need to wear hearing protection for more than intermittent visits.

The ability of a material or product to block sound at a specific frequency is its transmission loss (TL). Transmission loss ranges from 0 dB, for materials that provide no reduction in sound engery, to greater than 70 decibels (dB) for materials that provide the greatest reduction in sound energy. Tranmission loss is generally measured at frequencies of 125, 250, 500, 1,000, 2,000 and 4,000 Hertz (Hz).  Sound transmission class (STC) is a single-number rating used to describe the ability of a material to act as a sound barrier for sounds from 125 to 4,000 Hz.  In addition to blocking sound energy, most barriers and enclosures will also absorb sound. The fraction of sound energy that is absorbed is called the sound absorption coefficient. A particular material’s noise reduction coefficient (NRC) is the average sound absorption coefficient, measured at 250, 500, 1,000 and 2,000 Hz. An NRC of 0 means the surface is a perfect reflector of sound and an NRC of 1.0 means the surface is a perfect absorber of sound. It is possible to have an NRC above 1.0.

Kinetics Noise Control

Acoustical Louvers

• Construction Materials: steel, aluminum, baked enamel
• Applications: building vents, generator room vents, barrier wall systems, acoustical enclosure ventilation, commercial and industrial duct systems
• Transmission Loss: from 5 dB at 125 Hz to 31 dB at 8,000 Hz

Sound Transmission Loss

Sound Barrier Walls

• Construction Materials: steel, foam, fiberglass
• Absorption Material: NOISEBLOCK^TM, 2 or 4 inches thick
• Applications: utilities, transportation/highways, rooftop equipment, residential noise compliance, custom designed for each application

Sound Absorption Coefficients

Sound Transmission Loss

Rigid Enclosures

• Construction Materials: steel, foam, fiberglass, mineral wool
• Absorption Material: NOISEBLOCK^TM
• Applications: pumps, compressors, saws, shakers, milling machines, process equipment, custom designed for each application

Sound Absorption Coefficients

Sound Transmission Loss

Sound Fighter Systems Noise Control

HVAC Equipment Sound Wall

• Construction Material: steel exterior with a asphalt core or a cement board backing
• Absorption Material: LSE, mineral fiber
• Noise Reduction Coefficient: 1.05
• Transmission Loss: up to 33 dB
• Applications railroad, aircraft, construction, highways, HVAC, manufacturing and industrial, utilities, oil and gas, custom designed for each application

The LSE Absorptive Noise Barrier System is assembled in panels and locked into place within a steel skeleton.

Eco Sound Barrier Noise Control

Eco Sound Barrier

• Construction Material: steel
• Absorption Material: foam
• Applications: sound barriers custom designed for each application

The Eco Sound Barrier is a reflective barrier that incorporates a specially designed foam core, created by CENTRIA, to absorb sound. The barriers are assembled in panels, then locked into place within a steel skeleton. Optional insulation wrapping is available for greater sound absorption.

Sound Transmission Loss

Unger Technologies Steel Sound Enclosures

Sound Enclosure

• Construction Material: steel
• Absorption Material: absorption foam or mineral wool
• Applications: custom designed for each application

The Unger Sound Enclosure uses specially designed absorption materials and is assembled in panels and held in place within a steel skeleton.

Sound Absorption Coefficients

Sound Transmission Loss

Lower noise levels are expected to reduce stress and fatigue, and increase the concentration and mental performance of workers. Improved worker health, comfort and concentration may lead to greater productivity. Reduced sound levels can also lower the risk of accidents as communication among workers is easier and more effective. The number of noise-related complaints received, particularly from the impacted community may be reduced, thereby increasing productivity.

The use of diesel and especially gas-powered equipment poses the risk of carbon monoxide exposure, especially in enclosures and areas where airflow is reduced. Steps to control exposure are important because the gas is invisible, odorless and tasteless. Poisoning by carbon monoxide can occur quickly indoors or in enclosures, but working outdoors does not ensure operators won’t be overcome. Small, inexpensive personal monitors should be worn by the operator to warn of unacceptable exposures. Equipment should not be left idling to cut down on carbon monoxide and to conserve fuel.

As is the case with any construction equipment, users should follow manufacturer safety recommendations and comply with any applicable local, state or federal regulations.

Andrew Kingston, Michael R. Cooper and Bruce Lippy - The Lippy Group, LLC

• General Labor
  • Compact earth
    • Noise
  • Jackhammer rock and concrete surfaces
    • Noise
  • Operate concrete mixers, pumps and fire proofing sprayers
    • Noise
  • Operate earth boring machines
    • Noise
  • Operate pavement cutters and concrete grinders
    • Noise
  • Pave and patch concrete and asphalt
    • Noise