Exposure & Controls

Exposure to Noise is measured in units of sound pressure levels called decibels, named after Alexander Graham Bell, using an A-weighted sound levels (dBA). The A-weighted sound levels closely match the perception of loudness by the human ear. Decibels are measured on a logarithmic scale which means that a small change in the number of decibels results in a huge change in the amount of noise and the potential damage to a person's hearing. There are several ways to control and reduce worker exposure to noise in a workplace where exposure has been shown to be excessive. Engineering controls involve modifying or replacing equipment, or making related physical changes at the noise source or along the transmission path to reduce the noise level at the worker's ear. Examples of inexpensive, effective engineering controls include some of the following: Choose low-noise tools and machinery; Maintain and lubricate machinery and equipment (e.g., oil bearings); Place a barrier between the noise source and employee (e.g., sound walls or curtains); and Enclose or isolate the noise source. Administrative controls are changes in the workplace or schedule that reduce or eliminate the worker exposure to noise. Examples include: Operating noisy machines during shifts when fewer people are exposed; Limiting the amount of time a person spends at a noise source; Providing quiet areas where workers can gain relief from hazardous noise sources; and Controlling noise exposure through distance is often an effective, yet simple and inexpensive administrative control. Specifically, for every doubling of the distance between the source of noise and the worker, the noise is decreased by 6 dBA.

The following references provide information on measuring noise exposure and recognizing and controlling workplace noise hazards.

• OSHA Technical Manual (OTM). OSHA Directive TED 01-00-015 [TED 1-0.15A], (1999, January 20).
  
  
  • Technical Equipment. Contains information on noise monitors and meters, including descriptions and techniques for the use of sound level meters and dosimeters.
    
    
  • How do I evaluate noise exposure? OSHA Noise and Hearing Conservation eTool.
    
    
• Health Hazard Evaluations: Noise and Hearing Loss, 1986-1997. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 99-106, (1998, November). Also available as a 72 KB PDF, 12 pages. Presents summaries, by industry, of different health hazard evaluations performed for exposures to noise.
  
  
• Industrial Noise Control Manual. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 79-117, (1978, December). Contains essential information about noise control technology, as well as a collection of 61 case histories describing successful noise control projects.
  
  
• Noise Reduction Ideas Bank. Washington State Department of Labor & Industries. Searchable database containing engineering controls for noise.
  
  
• Case studies. Health and Safety Executive (HSE), United Kingdom.  Extensive index of noise control case studies from HSE.
  
  
• Controlling Noise on Construction Sites [278 KB PDF, 19 pages]. Laborer's Health and Safety Fund of North America (LHSFNA). Describes how to evaluate and control noise hazards at construction sites. Additional resources on noise are also provided. [Best Practices Guide]
  
  
• Occupational Noise-Induced Hearing Loss in Australia - Overcoming barriers to effective noise control and hearing loss prevention [1 MB PDF, 207 pages]. Safe Work Australia, (2010, August).
  
  
• Buy-Quiet Process Roadmap. EARLAB, National Aeronautics and Space Administration (NASA) Auditory Demonstration Laboratory.
  
  
• Online Noise Databases. EARLAB, National Aeronautics and Space Administration (NASA) Auditory Demonstration Laboratory.
  
  
• Occupational exposure to noise: evaluation, prevention and control. World Health Organization (WHO). Provides an in depth look at all aspects of noise.
  
  
  • Engineering Noise Control [1 MB PDF, 52 pages]. Provides an in depth look at noise control and has multiple examples of  designs of various noise controls.
    
    
• Industrial Noise Control, Fundamentals and Applications. Bell, Lewis H. and Bell, Douglas H.  Marcel Decker, Inc., (1994).

Accessibility Assistance: Contact the OSHA Directorate of Technical Support and Emergency Management at (202) 693-2300 for assistance accessing PDF materials.