Measuring earplug noise attenuation: A comparison of laboratory and field methods.

Hearing protection device (HPD) fit-testing is a recommended best practice for hearing conservation programs as it yields a metric of the amount of attenuation an individual achieves with an HPD. This metric, the personal attenuation rating (PAR), provides hearing health care, safety, and occupational health personnel the data needed to select the optimal hearing protection for the occupational environment in which the HPD will be worn. Although commercial-off-the-shelf equipment allows the professional to complete HPD fit tests in the field, a standard test methodology does not exist across HPD fit-test systems. The purpose of this study was to compare the amount of attenuation obtained using the "gold standard" laboratory test (i.e., real-ear attenuation at threshold [REAT]) and three commercially available HPD fit-test systems (i.e., Benson Computer Controlled Fit Test System [CCF-200] with narrowband noise stimuli, Benson CCF-200 with pure tone stimuli, and Michael and Associates FitCheck Solo). A total of 57 adults, aged 18 to 63, were enrolled in the study and tested up to seven earplugs each across all fit-test systems. Once fitted by a trained member of the research team, earplugs remained in the ear throughout testing across test systems. Results revealed a statistically significant difference in measured group noise attenuation between the laboratory and field HPD fit-test systems (p < .0001). The mean attenuation was statistically significantly different (Benson CCF-200 narrowband noise was +3.1 dB, Benson CCF-200 pure tone was +2.1 dB, and Michael and Associates FitCheck Solo was +2.5 dB) from the control laboratory method. However, the mean attenuation values across the three experimental HPD fit-test systems did not reach statistical significance and were within 1.0 dB of one another. These findings imply consistency across the evaluated HPD fit-test systems and agree with the control REAT test method. Therefore, the use of each is acceptable for obtaining individual PARs outside of a laboratory environment.

Personal attenuation ratings versus derated noise reduction ratings for hearing protection devices.

National and international regulatory and consensus standards setting bodies have previously proposed derating hearing protector ratings to provide a better match between ratings determined in a laboratory and the real-world measurements of attenuation for workers. The National Institute for Occupational Safety and Health has proposed a derating scheme that depends upon the type of protector. This paper examines four real-world studies where personal attenuation ratings (PARs) were measured at least twice, before and after an intervention in earplug fitting techniques. Results from these studies indicate that individualized earplug fitting training dramatically improves a worker's achieved PAR value. Additionally, derating schemes fail to accurately predict the majority of achieved PARs. Because hearing protector fit testing systems are now readily available for use in the workplace, personal attenuation ratings provide a better estimate of worker noise exposures and are able to identify those persons who need additional instruction in fitting hearing protection devices.

How hearing conservation training format impacts personal attenuation ratings in U.S. Marine Corps Training Recruits.

OBJECTIVE: The purpose of this fit-testing study in the field was to systematically compare three Hearing Protection Device (HPD) fit-training methods and determine whether they differ in the acquisition of HPD fitting skill and resulting amount of earplug attenuation. DESIGN: Subjects were randomly assigned to receive HPD fit-training using one of three training methods: current, experiential HPD (eHPD), and integrated. Personal Attenuation Ratings (PARs) were acquired via HPD fit-testing and used to verify attenuations pre- and post-training. STUDY SAMPLE: US Marine training recruits (n = 341) identified via HPD fit-testing for remedial HPD fit-training and assigned to three cohorts. RESULTS: The post-training HPD fit-test passing rate differed by training method, with pass rates ranging from 50% (current) to nearly 92% (eHPD). The difference between group delta PAR values were significantly higher (>9 dB) in both the eHPD and integrated methods compared to the current method. CONCLUSION: The HPD fit-training methods that teach "what right feels like" (eHPD and integrated) provided a greater number of trainees with the skill to achieve noise attenuation values required for impulse noise exposures encountered during basic training. The attenuation achieved by those methods was significantly greater than the current training method.

Defining Normal Balance for Army Aviators.

INTRODUCTION: One challenge clinicians face is determining when a military Service Member (SM) can return to duty after an injury that affects the postural control. The gold standard to measure postural control is the Sensory Organization Test (SOT). This test measures the amount of sway present in an individual's static stance that may be used to examine range of function and monitor recovery from injury. Normative values currently available were developed using a sample of clinically normal adults from the general population (i.e., civilian non-aviator). Previous research suggests that these values should not be used as a comparative cohort for high-performing populations in the military. However, normative values, specific to military SMs, do not exist. The aim of this study was to develop a normative clinical database for functional balance (i.e., the SOT) for military-trained aviators, an occupational specialty that may consist of high performers. MATERIALS AND METHODS: Forty-three U.S. Army trained aviators, between 23 and 40 years old with medical clearance for flight operations from the Fort Rucker, Alabama area community consented and participated in this study. The SOT was delivered using the NeuroCom SMART EquiTest Clinical Research System with the Data Acquisition Toolkit (version 9.3). RESULTS: A statistically significant (p < 0.01) difference between the study cohort of Army-trained aviators and the publically available general civilian normative values was found for the more challenging conditions, in which the force plate was not fixed (i.e., conditions four through six). The study cohort of Army-trained aviators were found to have a higher equilibrium score in each of these three conditions. Similarly, a significant difference (p < 0.01) between the two cohorts was found on the visual and vestibular sensory analysis ratios, and the visual preference scores (i.e., greater reliance upon visual information in the maintenance of balance). The study cohort were found to have a higher ratios (i.e., greater dependence upon these sensory cues) in each of these conditions. CONCLUSION: Army-trained aviators are high-functioning performers whose SOT scores differ from that of the general civilian population, particularly for the more challenging test conditions. New normative values were developed from this study population. Use of the developed normative values could be used as a comparative cohort in screening aviators who are recovering from injuries that affect postural stability.

Hearing Loss and Tinnitus in Military Personnel with Deployment-Related Mild Traumatic Brain Injury.

The objective of this study was to analyze differences in incidence and epidemiologic risk factors for significant threshold shift (STS) and tinnitus in deployed military personnel diagnosed with mild traumatic brain injury (mTBI) due to either a blast exposure or nonblast head injury. A retrospective longitudinal cohort study of electronic health records of 500 military personnel (456 met inclusion criteria) diagnosed with deployment-related mTBI was completed. Chi-square tests and STS incidence rates were calculated to assess differences between blast-exposed and nonblast groups; relative risks and adjusted odds ratios of developing STS or tinnitus were calculated for risk factors. Risk factors included such characteristics as mechanism of injury, age, race, military occupational specialty, concurrent diagnosis of posttraumatic stress disorder (PTSD), and nicotine use. Among blast-exposed and nonblast patients, 67% and 58%, respectively, developed STS, (P=.06); 59% and 40%, respectively, developed tinnitus (P<.001). Incidence of STS was 24% higher in the blast-exposed than nonblast group. Infantry service was associated with STS; Marine Corps service, PTSD, and zolpidem use were associated with tinnitus. Unprotected noise exposure was associated with both STS and tinnitus. This study highlights potential risk factors for STS and tinnitus among blast-exposed and nonblast mTBI patient groups.