Noise - Occupational

Noise -- Occupational

Overview

Program Managers (PM) should strive to eliminate or reduce personnel exposure to hazardous noise associated with operation and maintenance of the systems whenever possible. Noise can result in behavioral and physiological impacts to personnel (e.g., damage to the ear, communication problems, difficulty understanding speech, annoyance, difficulty concentrating, reduced performance, etc.). Hearing loss is one of the most common work-related illnesses in the U.S., according to the National Institute for Occupational Safety and Health (NIOSH). Both NIOSH and the Department of Veterans Affairs (VA) report that millions are spent annually on worker’s compensation for hearing loss disability. According to the NIOSH, nationally, every year there is approximately $242 million in compensation and approximately 22 million U.S. workers exposed to hazardous noise levels at work. The VA has estimated that from 1977 to 2006, the cost of hearing loss for all veterans was approximately eight billion dollars, and that costs are approaching one billion dollars per year (Source: NATO Science and Technology Organization Report #RTO-TR-HFM-147).

If the acquisition of a system is likely to generate noise during operation, then determining the noise footprint of the system is critical as part of the design and systems engineering process, especially during technological development and engineering and manufacturing development (See DoD Design Criteria Standards for Noise [MIL-STD-1474D CH1]). While MIL-STD-1474D CH1 is the DoD standard for addressing many components of noise generation, risk determination, and noise reduction measures, PMs and system engineers should also consider other relevant guidance as necessary. American Standards Institute (ANSI) Standards (such as ANSI/ASA S12.X documents) and Component-specific guidance should be consulted during the occupational noise assessment process as needed.

The system’s noise attributes and footprint are used in determining the hazards and risks posed to personnel during test, operation, and maintenance. System engineers should strive to eliminate and reduce personnel exposure to high levels of noise (even if the source of hazardous noise cannot be eliminated). This ultimately contributes to preventing occupational hearing loss through technology and engineering design solutions, improved operational and maintenance procedures, and lastly personal hearing protective devices.

Occupational Noise Considerations

Noise exposure can be described by the intensity of the noise, its frequency, and its duration. Intensity of noise reflects the loudness of the sound, while the frequency of the noise is reflected in how high or low pitched the noise is. Noise levels [measured in decibels A-weighted (dBA)] and exposure times are key factors in determining the potential affects to personnel from hazardous noise. DoD considers any sound above 84 dBA as hazardous, or having the potential to cause hearing loss. See the Noise - Far-Field Topic on this site for additional details regarding noise and metrics.

Many DoD systems and processes introduce personnel to excessive noise (e.g., aircraft carrier deck operations, shipboard environments, tanks, artillery and gunnery systems, environmental control/cooling systems, support equipment, etc.). Acquisition PMs should design systems that will minimize hazardous noise levels or minimize sound to less than 84 dBA. There are various factors to consider when determining the potential for noise impacts to personnel. MIL-STD-1474D CH1 provides details for noise limits in the systems engineering design process. The standard outlines acquisition requirements and guidance for noise-related issues in the design of facilities or equipment as it relates to personnel health and safety. PMs and ESOH practitioners should review this document when acquiring systems that generate noise. For example, Clause #5 of MIL-STD-1474D CH1 Foreword states that, “Whenever feasible, all new equipment, whether newly designed or purchased, shall emit the lowest possible noise levels.” Component-specific policies and noise reduction programs should also be consulted to help structure the system design process on what may be achievable technically and operationally to reduce generated noise levels and personnel exposure risks.

The Noise Levels table provides an example of representative noise levels associated with different sources/operations.

Table 1. Noise Level Representations

Exposure to noise at levels greater than 84 dBA for more than an eight-hour time period needs to be mitigated using engineering controls or personal hearing protective devices. The following hierarchy of controls to mitigate occupational health noise hazards predominantly applicable to the DoD acquisition process includes, but are not limited to, the following (See MIL-STD-1474D CH1 and the National Institute for Occupational Safety and Health (NIOSH) Engineering Controls Program for additional information):

• prevent or contain the escape of the noise agent at its source (engineering control)
• control exposure by relocating the worker to a safe area (administrative controls)
• control the exposure with barriers between the worker and the hazard (personal protective equipment)

This hierarchy is aligned with the MIL-STD-882E system safety order of precedence – first, influence the design and then incorporate administrative controls and personal protective controls when other forms of mitigation are not possible. Noise measurements should be taken as early as possible in the design/engineering phases to determine if additional noise mitigation measures are needed.

PMs, system engineers, and ESOH practitioners should consider a wide range of noise-related issues during the design and acquisition process. The following represents some considerations with regard to eliminating and controlling occupational noise during the system design process:

• identify all noise sources that contribute to the overall noise level generated by the system
• evaluate technology solutions and integrate where technically and economically feasible (e.g., integrated power systems, dampners, chevrons on aircraft engines, mufflers, low noise generators, quiet-run devices, or other system-specific noise reduction systems identified by the system PM or system engineers)

• isolate or insulate (sound proof) noise (e.g., acoustic absorption, acoustic insulation, advanced acoustic materials and coatings, physical barriers, or moving the noise source further from receptors, if feasible)

• improve hearing protection devices
• consult with ESOH staff to determine acoustical-reduction needs based on the noise generated by the system