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Environmental Laws and Their Implications
Published in J.K. Yates, Daniel Castro-Lacouture, Sustainability in Engineering Design and Construction, 2018
J.K. Yates, Daniel Castro-Lacouture
The EPA regulates hearing protection devices (HPDs) through the Labeling of Hearing Protection Devices Regulation (40CFR, Part 211, Subpart B) (Occupational Health and Safety Administration 2007). The devices regulated by the EPA include earplugs, earmuffs, and communication headsets, all of which are used routinely at construction jobsites. Hearing protection devices are rated by the maximum decibel level they protect the user from and their effectiveness in reducing unwanted noise.
Human Hearing and Noise Criteria
Published in David A. Bies, Colin H. Hansen, Carl Q. Howard, Engineering Noise Control, 2018
David A. Bies, Colin H. Hansen, Carl Q. Howard
It is important that hearing protection devices are always worn during exposure to high noise levels, as even short periods of not wearing protection markedly reduces their effectiveness. Figure 2.22 shows the effective noise reduction of hearing protection devices that could provide nominal noise reductions of 30, 25, 20, 15, 10 dB, as a percentage of the time worn during exposure to loud noise. As an example, say a person is issued with a pair of high-grade earmuffs that are rated to provide 30 dB of noise reduction. However, the user only wears the device for 95% of the time during exposure to loud noise, which would be equivalent to having the earmuffs removed for only 24 minutes of an 8 hour shift. As shown in Figure 2.22 by the dotted curve, the effective noise reduction that the earmuffs provides is now only 13 dB, which is 17 dB less than expected! The MATLAB script, plot_effective_NR_vs_time.m, used to plot Figure 2.22 is available for download from MATLAB scripts for ENC (2017).
Personal Hearing Protection
Published in Lewis H. Bell, Douglas H. Bell, Industrial Noise Control, 2017
Lewis H. Bell, Douglas H. Bell
There are two basic types of hearing protection devices: earplugs and earmuffs. Earplugs are inserted into the ear canal. Earmuffs cover the outer ear as an acoustical shield or barrier. We shall elaborate on each type.
Noise exposures and perceptions of hearing conservation programs among wildland firefighters
Published in Journal of Occupational and Environmental Hygiene, 2019
George Broyles, Chucri A. Kardous, Peter B. Shaw, Edward F. Krieg
Statistical analysis determined which of the explanatory variables had a significant impact on the outcome variables, the TWA for noise for OSHA’s PEL and for NIOSH’s REL. The explanatory variables were noise perception (very low, low, moderate, high, and very high) by the firefighter, type of HPD (earplugs, earmuffs, double protection, or other forms of protection), received training in HPD use (yes/no), having a baseline test (yes/no), having a yearly audiogram (yes/no), and participating in a hearing conservation program (yes/no). Hearing protection devices were categorized based on the response of WLFFs into five different categories: insert earplugs; banded or canal earplugs; earmuffs; double hearing protection such as earmuffs worn over earplugs; and other for electronic or level-dependent hearing protectors). The data were modeled using SAS’s PROC MIXED procedure (SAS Institute, Cary, NC). The reason for employing mixed models was that, in a number of instances, the same firefighter received repeated measurements. Restricted maximum likelihood (REML) estimation was used with the Kenward-Roger denominator degrees of freedom; the covariance structure was variance components. Initially researchers ran the full model with all six explanatory variables; then this model was reduced by eliminating terms for which p > 0.10 as judged by F-tests. The results were based on 134 observations; the rest were not used due to missing data. Mixed models were used for individual observations. However, for the box plots in Figure1, with repeated noise exposure for an individual WLFF within the same work category, individual WLFF’s exposure measurements were averaged so that there was only one data point for each individual in each separate work category.