U.S. flag An official website of the United States government.
Official websites use .gov

A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS

A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

i

Rating the Performance of Active Noise Cancellation Devices

Public Domain


Details

  • Personal Author:
  • Description:
    Hazardous noise exposure can be a threat to the human auditory system; one that some workers contend with every day of their working career. The noise exposures vary in level, duration, and spectra. When engineering and administrative controls do not adequately protect workers, hearing protection devices (HPDs) must be used to reduce noise exposures. HPDs come in all shapes and sizes and can be worn in the ear (earplugs and canal caps), around the ear (earmuffs and headsets), or in combination. HPDs are provided to reduce the level of hazardous noise; this reduction can be achieved with passive HPDs or with HPDs that have built-in active noise cancellation (ANC), sometimes called active noise reduction technology. Devices with ANC technology are designed to increase the level of protection by actively reducing the level of low-frequency noise (typically at 500 Hz and below). ANC technology works by detecting noise under the HPD and generating an equal, but opposite phase signal to actively cancel the level of noise at the ear. This technology is beneficial in enhancing attenuation in the low-frequency range where passive HPD capabilities are sometimes limited. ANC can improve attenuation for workers in environments with high levels of low-frequency noise, such as rotary wing aircraft, propeller aircraft, power generation, wood finishing, and newspaper press facilities (Karplus & Bonvallet, 1958). When HPDs are being selected for workers who need them, certain factors should be considered: the type of noise that the workers are exposed to, appropriateness for that particular noise environment, cost, logistics, comfort, and maintenance. Performance ratings can indicate which HPD is appropriate for a specific noise environment. Currently, the Noise Reduction Rating (NRR) is the only rating required by law in the United States (US) (EPA, 1979). NRR only describes the passive performance HPDs, which in the case of ANC devices, means when the electronics are turned off. This single number rating does not provide frequency specific information to the user and it was designed to be applied directly to C-weighted noise level measurements. The US scientific community has developed new performance ratings, described in detail in ANSI S12.68, that provide more accurate ratings for a variety of HPDs, including those with ANC technology. For a study of ANC performance in HPDs, four ANC headsets were selected for this study: Bose A20, Telex Stratus HeliXT, Pilot DNCXL PA1779T, and Sennheiser HMEC250. These circumaural headsets were commercially available and were commercially purchased at similar price points. Noise attenuation performance measurements were collected at Wright-Patterson Air Force Base in Dayton, Ohio. Ten persons (five males and five females) volunteered for this study. They ranged in age from 18 to 24 years old. All subjects had hearing threshold levels of 15 dB or better from 125 to 8000 Hz. In summary, the results of this study demonstrate how important test data are to understanding the attenuation performance of an HPD. Devices with ANC technology are no exception. The results show how variable the results can be for devices using the same technology. For a lower-attenuation headset, the application may be better suited to a lower noise-exposure environment, whereas a high-attenuation, isolating headset is better suited to an environment with higher noise levels. The consumer needs both passive and active performance ratings to choose the HPD appropriate for a particular noise exposure. NRSA and NRSG ratings provide new metrics that can be used in the estimating of the level of A-weighted noise at the ear under the HPD. [Description provided by NIOSH]
  • Subjects:
  • Keywords:
  • ISSN:
    1083-7388
  • Publisher:
    National Hearing Conservation Association
  • Document Type:
    Text
  • Genre:
  • Place as Subject:
  • CIO:
    National Institute for Occupational Safety and Health (NIOSH)
  • Division:
    DART - Division of Applied Research and Technology
  • Topic:
    Workplace Safety & Health
  • Location:
    North America
  • Pages in Document:
    13-16
  • Volume:
    34
  • Issue:
    1
  • NIOSHTIC Number:
    nn:20050394
  • Citation:
    Spectrum 2017 Jul; 34(1):13-16
  • Contact Point Address:
    Hilary L. Gallagher, Air Force Research Laboratory, 2610 Seventh St., Bldg 441, WPAFB, OH 45433
  • Email:
    hilary.gallagher.1@us.af.mil
  • Federal Fiscal Year:
    2017
  • Peer Reviewed:
    False
  • Source Full Name:
    Spectrum: the National Hearing Conservation Association newsletter
  • Collection(s):
  • Main Document Checksum:
    urn:sha-512:f137c1d44d8fc9b2c6a27c1540396e94cea61cce57d07a8d74b697edc55355fcb79fb36713815d2876db65c54f41d9767daac53870015b8b4845adcbd97d9982
  • Download URL:
  • File Type:
    Filetype[PDF - 503.97 KB ]
PREVIOUS
ON THIS PAGE
Details
CDC STACKS serves as an archival repository of CDC-published products including scientific findings, journal articles, guidelines, recommendations, or other public health information authored or co-authored by CDC or funded partners.

As a repository, CDC STACKS retains documents in their original published format to ensure public access to scientific information.
BACK TO TOP