Low-Cost Earmuff Shown to Significantly Reduce Cast-Saw Noise.

Hearing protection devices reduce cast-saw noise. It would be helpful to identify the devices that are both effective and economical. Prior studies have shown that expensive noise-reduction headphones significantly reduced the anxiety associated with cast removal with a powered oscillating saw. The cost of such headphones, however, is a drawback for some practices and hospitals. It would be helpful to determine whether lower cost ear protection can provide effective cast-saw noise reduction. In addition, it is unclear whether the noise reduction ratings (NRRs), the average sound-level reduction provided by a hearing protection device in a laboratory test, provided by manufacturers accurately characterize the effectiveness for reducing cast-saw noise. Note that noise-cancelling devices do not carry an NRR because they are not designed as hearing protectors. Five ear protection devices with different NNRs were tested. The devices varied greatly in cost and included earplugs, low-cost earmuffs, and noise-cancelling headphones. To standardize the evaluation, each device was fitted to an acoustic mannequin with high-fidelity ear microphones while a fiberglass spica cast was cut. An additional test was run without hearing protection as a control. The low-cost devices significantly reduced the saw noise, with the exception of earplugs, which had highly variable performance. The noise reduction was similar between low-cost earmuffs and the high-cost earphones when the noise-cancelling feature was not active. Active noise cancelling provided further reductions in the noise level. Patients can experience high anxiety during cast removal. The current study shows that low-cost earmuffs significantly reduce cast-saw noise. Patient care settings may be more likely to offer hearing protection that is one twenty-fifth the cost of noise-cancelling headphones. An NRR appears to be a reliable guide for selecting hearing protection that reduces cast-saw noise.

The Impact of Earplugs and Eye Masks on Sleep Quality in Surgical ICU Patients at Risk for Frequent Awakenings.

OBJECTIVES: Sleep disturbances may contribute to the development of delirium, prolonged ICU stay, and increased mortality. There is conflicting data on the effectiveness of earplugs and eye masks for sleep promotion in the ICU. This study evaluates the impact of earplugs and eye masks on sleep quality in postoperative surgical ICU patients at risk for frequent awakenings. DESIGN: Prospective randomized controlled trial. SETTING: Surgical ICU within the University of Texas Southwestern Medical Center. PATIENTS: Adult, female patients admitted to the surgical ICU requiring hourly postoperative assessments following breast free flap surgery between February 2018 and October 2019. INTERVENTIONS: Patients were randomized into an intervention group or a control group. The intervention group received earplugs and eye masks in addition to standard postoperative care, whereas the control group received standard postoperative care. MEASUREMENTS AND MAIN RESULTS: The primary outcome was overall sleep quality assessed via the Richards-Campbell Sleep Questionnaire. Secondary outcomes of patient satisfaction and rates of ICU delirium were assessed with a modified version of the Family Satisfaction in the ICU survey and the Confusion Assessment Method for the ICU. After a planned interim analysis, the study was stopped early because prespecified criteria for significance were attained. Compared with the control group's average Richards-Campbell Sleep Questionnaire total score of 47.3 (95% CI, 40.8-53.8), the intervention group's average Richards-Campbell Sleep Questionnaire total score was significantly higher at 64.5 (95% CI, 58.3-70.7; p = 0.0007). There were no significant between-group differences for Confusion Assessment Method for the ICU scores or modified Family Satisfaction in the ICU survey scores. CONCLUSIONS: These results suggest that earplugs and eye masks are effective in improving sleep quality in ICU patients undergoing frequent assessments. The results strengthen the evidence for nonpharmacologic sleep-promoting adjuncts in the ICU.

The insertion loss distribution function of an ear plug, and its implications for the ear plug acceptability.

INTRODUCTION: In order to establish the acceptability of a hearing protector device (HPD) used in a given noisy environment, two key elements must be known with the highest possible accuracy: the insertion loss of the HPD and the associated variability. Methods leading to objective field measurements of insertion loss have become widely available in the last decade and have started to replace the traditional subjective "Real-Ear Attenuation at Threshold" (REAT) laboratory measurements. The latter have long been known to provide a gross overestimate of the attenuation, thus leading to a strong underestimate of the worker's exposure to noise. METHODS: In this work we present objective measurements of the insertion loss of an ear plug, carried out using the E-A-Rfit procedure by 3M on a large sample of 36 female and 64 male subjects. This large number of independent measurements has been exploited to calculate the distribution function of effective noise levels, that is noise levels that take into account the use of the HPD. The knowledge of the distribution function has in its turn allowed the calculation of the uncertainty on the effective noise levels. RESULTS: This new estimate of uncertainty (6 to 7 dB) is significantly larger than most previous estimates, which range between 4 and 5 dB when using objective data but with an improper uncertainty propagation, and around 3 dB when using REAT subjective data. We show that the revised new estimate of uncertainty is much more realistic as it includes contributions that are missed by the other methods. CONCLUSIONS: By plugging this revised estimate of uncertainty into the criterion for checking the acceptability of the HPD, a better assessment of the actual protection provided by the HPD itself is possible.

Hearing protective devices and its role in Noise induced hearing loss: An interventional study.

This Quasi experimental study was conducted with the objective to determine the effectiveness of preventive measures including awareness programme and use of hearing protective devices (HPDs) for the prevention and control of Noise Induced Hearing Loss among Oil and Gas field workers from January 2015 to March 2016. A total of 120 workers were selected by convenient sampling, and subjected to pure tone audiometry (PTA) to obtain hearing thresholds followed by intervention with HPDs and retesting a year later. The Mean pure tone thresholds on first visit was 21.19±11.60 dB in right and 24.66±13.26 dB in left ear, while means at second visit (after one year) were 20.65±10.44 dB and 21.45±11.74 dB for the right and left ears respectively with statistically significant difference (p=0.001) for the left ear on t-test. However the difference of frequency and percentage of the participants with normal and reduced hearing at both visits was significant (chi square P=0.001). Hearing protective devices (HPDs) are an effective means to prevent NIHL in workers of oil and gas fields.

Consumer-Grade Headphones for Children: Limited Effectiveness of "Level Limiters" When Used With Portable or Home Media Players.

Consumer-grade headphones for children are frequently packaged or marketed with labels claiming incorporation of an output-level-limiting function. Six pairs of headphones, sold separately from devices with audio interfaces, were selected either from online recommendations or from "best rated" with a large online retailer, the opinions being expressed in 2018 to early 2019. The acoustic outputs in response to an internationally standardized test signal were measured through the ears of a head-and-torso simulator and referenced to equivalent A-weighted diffuse-field sound pressure levels. The headphones were tested with a variety of music capable sources found in a domestic environment, such as a mobile phone, tablets, laptop computer, and a home "hi-fi" CD player. To maintain likely homogeneity of the audio interface, the computer-based platforms were manufactured by either Apple™ or certified Android devices. One of the two Bluetooth-linked headphones exhibited level limiting with low distortion (i.e., a compression ratio well in excess of unity). None of the devices wired directly to an audio output performed distortionless level limiting: "limiting" was implemented by a reduction of sensitivity or mechanical limitations, so could be called "soft limiting." When driven by a laptop or CD player, some were still capable of producing output levels well in excess of "safe-listening" levels of 85 dB(A). Packaging labels were frequently ambiguous and imprecise.

Design of nonlinear active noise control earmuffs for excessively high noise level.

When exposed to high levels of noise, earmuffs are often used to avoid hearing loss. However, active noise control earmuffs may exhibit nonlinearities under excessive levels of noise, due to their low-power characteristics of the loudspeakers, and thus nonlinear control algorithms are required to improve the control performance. In this paper, an analytical model of a nonlinear active noise control earmuff is investigated. Based on this model, a robust state feedback control law is designed in the framework of linear matrix inequalities with respect to the parametric uncertainties of the loudspeaker and the limitation of control input. Then the backstepping approach is adopted to force the nonlinear part of the loudspeaker to track the derived state feedback signal and estimate the unknown parameters. Both recorded vehicle noise and multi-frequency noise are used to test the effectiveness of the proposed controller and the control performance is compared with that of a widely accepted nonlinear generalized functional link artificial neural network algorithm. Simulation results demonstrate that the proposed controller is capable of attenuating the interior noise and reducing harmonic and intermodulation distortions significantly.

Selection of Level-Dependent Hearing Protectors for Use in An Indoor Shooting Range.

The high sound pressure level generated by impulse noise produced in an indoor shooting range makes it necessary to protect the hearing of the people it affects. Due to the need for verbal communication during training at a shooting range, level-dependent hearing protectors are useful. The objective of this study was to answer the question of whether it is possible to properly protect the hearing of a shooting instructor using level-dependent hearing protectors. The noise parameters were measured in the places where the instructor was present at the shooting range. The division of a specific group of trained shooters into subgroups consisting of three or six simultaneously shooting individuals did not significantly affect the exposure of the shooting instructor to the noise. An assessment of noise reduction was carried out for eight models of earmuffs and two variants of earplugs, using computational methods for the selection of hearing protectors. Among the noise parameters, both the A-weighted equivalent sound pressure level and the C-weighted peak sound pressure level were taken into account. Depending on the assessment criterion adopted, a sufficient reduction in impulse noise was provided by either four or six out of the 10 hearing protectors included in the study.

Verificación de niveles de atenuación de protectores auditivos tipo copa en trabajadores del sector Hidrocarburos / Verifying the attenuation levels of earmuff hearing protectors in Oil & Gas workers / Verificando os níveis de atenuação dos protetores auditivos de abafador em trabalhadores de petróleo e gás

RESUMEN Objetivo Verificar los niveles de atenuación de dos tipos de protectores auditivos de copa bajo condiciones reales de operación. Métodos Se realizó un diseño experimental de medidas repetidas de los niveles de presión sonora al interior y exterior de los protectores auditivos, realizando mediciones de ruido bajo circunstancias habituales de trabajo para operadores de una planta de hidrocarburos. Posteriormente, se determinaron las diferencias entre los niveles de atenuación establecidos por el fabricante, los niveles de atenuación ajustados bajo el método recomendado por NIOSH y los niveles de atenuación obtenidos experimentalmente. Resultados Los valores de atenuación ofrecidos por los fabricantes difieren de los obtenidos experimentalmente, siendo estos últimos, menores en todos los casos del estudio. Los valores de atenuación de los protectores auditivos ajustados bajo el método NIOSH alcanzaron valores más cercanos a los experimentales. Conclusiones La variabilidad entre los valores de atenuación teóricos y experimentales, permiten establecer que las estimaciones de los niveles de atenuación obtenidos en condiciones controladas no consideran aspectos que en condiciones reales de uso afectan la eficiencia del protector auditivo. Este estudio plantea la necesidad de implementar programas integrales de protección auditiva, que permitan considerar variables asociadas a la eficacia del dispositivo en condiciones de uso, a través de la aplicación de pruebas de ajuste o en su defecto a través de la aplicación de los factores de ajuste sugeridos por NIOSH, con el fin de realizar una adecuada selección que permita alcanzar un control efectivo para el ruido.

ABSTRACT Objective To verify the attenuation levels of two types of earmuffs under real operating conditions. Materials and Methods A study with experimental design was carried out to obtain repeated measurements of the sound pressure levels inside and outside hearing protectors in a sample of workers of an oil and gas company working under normal process and exposure conditions. The results allowed determining differences between the attenuation levels established by the manufacturer, the adjusted attenuation levels under the NIOSH method, and the attenuation levels obtained experimentally. Results The attenuation values established by the manufacturers are lower than those ones obtained under actual use conditions in all cases evaluated. Likewise, the attenuation values of the hearing protectors, once adjusted under the NIOSH method, reached values much closer to those obtained experimentally. Conclusions The variability between theoretical attenuation values and experimental values allows concluding that the attenuation levels obtained under controlled laboratory conditions do not take into account certain characteristics that, based on their use, affect the efficiency of the hearing protection device. This study encourages the implementation of comprehensive hearing protection programs that consider variables such as hearing protection effectiveness, under real use conditions, by applying fit tests or other adjustment factors like the one suggested by NIOSH. This would ensure an adequate selection that aims at achieving an effective control of this risk factor.

RESUMO Objetivo Verifique os níveis de atenuação de dois tipos de protetores auriculares em condições reais de operação. Métodos Foi realizado um projeto experimental de medições repetidas dos níveis de pressão sonora dentro e fora dos protetores auditivos, fazendo medições de ruído em condições normais de trabalho para operadores de uma usina de hidrocarbonetos. Posteriormente, foram determinadas as diferenças entre os níveis de atenuação estabelecidos pelo fabricante, os níveis de atenuação ajustados pelo método recomendado pelo NIOSH e os níveis de atenuação obtidos experimentalmente. Resultados Os valores de atenuação oferecidos pelos fabricantes diferem daqueles obtidos experimentalmente, sendo este último menor em todos os casos do estudo. Os valores de atenuação dos protetores auditivos ajustados pelo método NIOSH atingiram valores mais próximos aos experimentais. Conclusões A variabilidade entre os valores de atenuação teórica e experimental permite estabelecer que as estimativas dos níveis de atenuação obtidos em condições controladas não consideram aspectos que, em condições reais de uso, afetam a eficiência do protetor auditivo. Este estudo levanta a necessidade de implementar programas abrangentes de proteção auditiva que permitam considerar variáveis associadas à efetividade do dispositivo em condições de uso, através da aplicação de testes de adaptação ou, na sua falta, através da aplicação de ajuste sugerido pelo NIOSH, a fim de fazer uma seleção adequada para obter um controle eficaz do ruído.(AU)

I'm Wearing My Hearing Protection - Am I Still At Risk for Hearing Loss? Lurking Ototoxins in the Military Environment.

OBJECTIVE: Information is summarized from the overall body of published literature regarding ototoxic chemicals encountered outside of clinical exposures, largely in occupational settings. While summarizing the most common non-pharmaceutical ototoxins, this review provides clinically relevant information and recommendations such that hearing health professionals may adopt a more comprehensive and appropriate diagnostic case history, test battery, documentation scheme, and education delivery. METHODS: Solvents, metals, and asphyxiants literature was reviewed using PubMed, national and international agency websites, and communications with known ototoxicity experts. RESULTS: Initial intentions to summarize the existing programs for occupational ototoxicity monitoring fell short when it was discovered that such programs have not yet formalized across the major oversight agencies in the United States. Instead, recommended guidance documents and fact sheets, which highlight existing occupational exposure limits and suggest monitoring and education are discussed. CONCLUSIONS: While evidence in humans is limited, potentially ototoxic substances are worthy of improved surveillance and further research to understand their ototoxic mechanisms, effects, and possible mitigation strategies. A triad approach of monitoring, protecting, and educating is recommended for effective prevention of hearing loss: the Department of Defense Hearing Center of Excellence's Comprehensive Hearing Health Program model employs such an approach.

Characterization of Protection Mechanisms to Blast Overpressure for Personal Hearing Protection Devices - Biomechanical Measurement and Computational Modeling.

Hearing damage induced by blast exposure is a common injury in military personnel involved in most operation activities. Personal hearing protection devices such as earplugs come as a standard issue for Service members; however, it is not clear how to accurately evaluate the protection mechanisms of different hearing protection devices for blast overpressures (BOP). This paper reports a recent study on characterization of earplugs' protective function to BOP using human cadaver ears and 3D finite element (FE) model of the human ear. The cadaver ear mounted with pressure sensors near the eardrum (P1) and inside the middle ear (P2) and with an earplug inserted was exposed to BOP in the blast test chamber. P1, P2, and BOP at the ear canal entrance (P0) were simultaneously recorded. The measured P0 waveform was then applied at the ear canal entrance in the FE model and the P1 and P2 pressures were derived from the model. Both experiments and FE modeling resulted in the P1 reduction which represents the effective protection function of the earplug. Different earplugs showed variations in pressure waveforms transmitted to the eardrum, which determine the protection level of earplugs.

A study of the real-world noise attenuation of the current hearing protection devices in typical workplaces using Field Microphone in Real Ear method.

BACKGROUND: Actual noise reduction of the earmuffs is considered as one of the main challenges for the evaluation of the effectiveness of a hearing conservation program. OBJECTIVE: The current study aimed to determine the real world noise attenuation of current hearing protection devices in typical workplaces using a field microphone in real ear (FMIRE) method. METHODS: In this cross-sectional study, five common earmuffs were investigated among 50 workers in two industrial factories with different noise characteristics. Noise reduction data was measured with the use of earmuffs based on the ISO 11904 standard, field microphone in real ear method, using noise dosimeter (SVANTEK, model SV 102) equipped with a microphone SV 25 model. RESULTS: The actual insertion losses (IL) of the tested earmuffs in octave band were lower than the labeled insertion loss data (p < 0.05). The frequency nature of noise to which workers are exposed has noticeable effects on the actual noise reduction of earmuffs (p < 0.05). The results suggest that the proportion of time using earmuffs has a considerable impact on the effective noise reduction during the workday. CONCLUSIONS: Data about the ambient noise characteristics is a key criterion when evaluating the acoustic performance of hearing protectors in any workplaces. Comfort aspects should be considered as one of the most important criteria for long-term use and effective wearing of hearing protection devices. FMIRE could facilitate rapid and simple measurement of the actual performance of the current earmuffs employed by workers during different work activities.

Development of the Warfighter's Hearing Health Instructional (WHHIP) Primer App.

The Warfighter's Hearing Health Instructional Primer (WHHIP) is a supplemental tool for military hearing conservation programs (MHCPs) and can be accessed by the warfighter on his/her own personal mobile phone. A gap was identified for a supplement to MHCPs that is easily accessible by warfighters to improve hearing health knowledge. The WHHIP aims to instruct the warfighter in best hearing health practices. To do so, four activities are included: Learn, Demos, HPD Check, and Glossary. Learn and Glossary allow the warfighter to scroll through various informational topics related to hearing conservation - including videos, descriptions of noise, and results of hearing tests. In the Demos activity, the warfighter can explore the difficulties that hearing loss and tinnitus pose to sound and speech identification. The HPD Check feature allows the warfighter to take a picture of the fit of hearing protection devices (HPDs) in his/her own ears then compare the images to ones that he/she had previously taken or of standard images of good fitting devices. The WHHIP is an easily accessed reference tool available for free via Google Play; if a warfighter has a question or concern regarding his/her hearing health, the WHHIP can be used to verify or improve knowledge.

Evaluating the effect of training along with fit testing on earmuff users in a Chinese textile factory.

A hearing protection fit testing was conducted on workers (n = 189) in a textile factory in southern China. The 3M E-A-Rfit Dual-Ear Validation System was used to measure the personal attenuation rating (PAR) on an over-the-head style earmuff at the work site. In addition, PARs were obtained several times throughout the same work shift to capture different fits on 39 workers. Follow-up visits were conducted in approximate 6-month or 12-month intervals to repeat the fit testing. Both the immediate and residual effects of training on the field attenuation of hearing protection devices obtained by workers, and the effects of training toward improving the attenuation and protection of earmuffs after a period of daily use, were observed. A questionnaire survey was used to assess the awareness of hearing health and motivation toward the use of earmuffs in a high temperature environment. The results showed that there were wide variations in PARs among the workers tested. The one-on-one training together with fit testing improved PAR and helped to reduce the negative impact caused by use of protective hair covers. Since earmuffs are often used for long periods of time (>1 year), repeating fit tests could be helpful in order to verify the attenuation received throughout their useful life.

The Impact of Annual Audiograms on Employee's Habits and Awareness Regarding Hearing Protection and Noise Induced Hearing Loss, On and Off the Job.

Noise-induced hearing loss occurs among workers across a wide spectrum of industries. The purpose of this study was to investigate whether annual hearing testing contributed to a change in employees' habits and awareness and aimed to evaluate the use of hearing protection at work and at home. Employees enrolled in a university's hearing conservation program (HCP) were anonymously surveyed regarding their hearing protection habits and awareness of noise exposures on and off the job using a Likert-type scale. Approximately half were "very much" concerned about hearing loss over time. Evidence supports that annual testing, part of the workplace HCP, also led over half of participants to change their habits at work and at home. Awareness of noise exposures increased both at home and at work with annual testing. Overall, the HCP in this particular setting was associated with improved on-the-job and home hearing protection use.

Caring for musicians' ears: insights from audiologists and manufacturers reveal need for evidence-based guidelines.

OBJECTIVE: This study investigated clinical care delivered to musicians in Australia by audiologists and manufacturers of musicians' hearing protectors (MHP). DESIGN: Audiologists with experience treating musicians were invited to complete a survey on their service delivery. A second survey was administered to manufacturers of MHPs. STUDY SAMPLE: Four manufacturers of MHP and 31 audiologists completed the surveys. Post hoc analyses were performed comparing the responses of audiologists with more versus less clinical experience; and those with and without musical training. RESULTS: There was considerable variation in the audiological care provided to musicians. Only one-third of audiologists performed pure-tone audiometry prior to MHP fitting, and there was little consistency across the sample in relation to impression taking, preferred attenuation or selection of canal length. There was also significant variation in the manufacturers' approach to MHP, each of whom provided different recommendations regarding preferred impression techniques and material viscosity. CONCLUSIONS: The results of this study reveal lack of consistency across the hearing healthcare sector with respect to care of musicians' hearing, with potential to impact upon the satisfaction with, and usage of, MHP. There is need for evidence-based, best practice guidelines and training to support clinical audiologists in providing optimal care.

Impact of earplugs and eye mask on sleep in critically ill patients: a prospective randomized study.

BACKGROUND: Poor sleep is common in intensive care unit (ICU) patients, where environmental factors contribute to reduce and fragment sleep. The objective of this study was to evaluate the impact of earplugs and eye mask on sleep architecture in ICU patients. METHODS: A single-center randomized controlled trial of 64 ICU patients was conducted from July 2012 to December 2013. Patients were randomly assigned to sleep with or without earplugs and an eye mask from inclusion until ICU discharge. Polysomnography was performed on the first day and night following inclusion. The primary outcome was the proportion of stage N3 sleep over total sleep time. Secondary outcomes were other descriptors of sleep and major outcome variables. RESULTS: In the intervention group, nine (30%) patients did not wear earplugs all night long. The proportion of N3 sleep was 21 [7-28]% in the intervention group and 11 [3-23]% in the control group (p = 0.09). The duration of N3 sleep was higher among the patients in the intervention group who wore earplugs all night long than in the control group (74 [32-106] vs. 31 [7-76] minutes, p = 0.039). The number of prolonged awakenings was smaller in the intervention group (21 [19-26] vs. 31 [21-47] in the control group, p = 0.02). No significant difference was observed between the two groups in terms of clinical outcome variables. CONCLUSIONS: Earplugs and eye mask reduce long awakenings and increase N3 duration when they are well tolerated. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02292134 . Registered on 21 Nov 2013.

Contemporary noise-induced hearing loss (NIHL) prevention.

Hearing impairment caused by noise, traditionally called - depending on the duration of exposure - acute or chronic acoustic trauma, includes, in addition to presbyacusis, the most common adult population of hearing impaired. In Poland - according to the report of the Central Statistical Office (GUS, 2011), the number of workers employed in NDN exceeded the noise level (85 dB) is about 200 thousand, the highest in the mining, metal and metal products production, textiles and wood production. According to the Regulation of the Council of Ministers of on June 30, 2009, on the list of occupational diseases (Journal of Laws No. 132, item 1115), it is defined as "bilateral permanent hearing loss of the cochlear or sensory-nerve type, expressed as an increase in hearing threshold of at least 45 dB in the ear better heard, calculated as an arithmetic mean for frequencies 1,2 and 3 kHz. Hearing impairments also occur in the military and police during field training and in combat where the source of acoustic injuries are firearms and pulse-inducing explosions (as in some industries) with high C peak levels (Lc peak) Time to rise to a maximum of <1 ms. The prevalence of loud music listening, particularly by personal stereo players, is also affecting children and adolescents with audiometric hearing loss, according to the World Health Organization (WHO) estimates of around 15-20%. The preventive action strategy is defined by the European Union legislation and the national implementing legislation that reduces or eliminates the risk and reduces (if not eliminated), taking into account available technical and organizational solutions to minimize the risk of hearing damage. If you can not reduce the noise levels with technical and organizational methods, you need individual hearing protectors. Ear protectors may be equipped with electronic systems with active noise reduction (which can improve low and medium frequency performance), adjustable attenuation (improves speech intelligibility and perception of warning signals), and wireless communication for verbal communication.

Acute Acoustic Trauma among Soldiers during an Intense Combat.

BACKGROUND: During military actions, soldiers are constantly exposed to various forms of potentially harmful noises. Acute acoustic trauma (AAT) results from an impact, unexpected intense noise ≥140 dB, which generates a high-energy sound wave that can damage the auditory system. PURPOSE: We sought to characterize AAT injuries among military personnel during operation "Protective Edge," to analyze the effectiveness of hearing protection devices (HPDs), and to evaluate the benefit of steroid treatment in early-diagnosed AAT injury. RESEARCH DESIGN: We retrospectively identified affected individuals who presented to military medical facilities with solitary or combined AAT injuries within 4 mo following an intense military operation, which was characterized with an abrupt, intensive noise exposure (July-December 2014). STUDY SAMPLE: A total of 186 participants who were referred during and shortly after a military operation with suspected AAT injury. INTERVENTIONS: HPDs, oral steroids. DATA COLLECTION AND ANALYSIS: Data extracted from charts and audiograms included demographics, AAT severity, worn HPDs, first and last audiograms and treatment (if given). The Student's independent samples t test was used to compare continuous variables. All tests were considered significant if p values were ≤0.05. RESULTS: A total of 186 participants presented with hearing complaints attributed to AAT: 122, 39, and 25 were in duty service, career personnel, and reservists, with a mean age of 21.1, 29.2, and 30.4 yr, respectively. Of them, 92 (49%) participants had confirmed hearing loss in at least one ear. Hearing impairment was significantly more common in unprotected participants, when compared with protected participants: 62% (74/119) versus 45% (30/67), p < 0.05. Tinnitus was more common in unprotected participants when compared with protected participants (75% versus 49%, p = 0.04), whereas vertigo was an uncommon symptom (5% versus 2.5%, respectively, p > 0.05). In the 21 participants who received steroid treatment for early-diagnosed AAT, bone-conduction hearing thresholds significantly improved in the posttreatment audiograms, when compared with untreated participants (p < 0.01, for 1-4 kHz). CONCLUSIONS: AAT is a common military injury, and should be diagnosed early to minimize associated morbidity. HPDs were proven to be effective in preventing and minimizing AAT hearing sequelae. Steroid treatment was effective in AAT injury, if initiated within 7 days after noise exposure.

Does Combat Hearing Preservation Equipment Affect Balance?

OBJECTIVES: (1) To investigate whether the occlusion effect and hearing attenuation produced by 3M Combat Arms Ear Plugs (CAEP) affects balance when compared to no hearing protection and (2) to investigate whether the occlusion effect and noise-canceling capabilities of the Nacre QuietPro system affects balance when compared to no hearing protection. METHODS: This prospective study collected pilot data for investigation of mechanisms of balance. 20 subjects with normal hearing and no vestibular dysfunction were tested with blackened goggles in three conditions-no hearing protection, CAEP, and with the Nacre QuietPro. RESULTS: A static posturogrpahy forceplate was used to measure center of gravity angular acceleration for a period of 20 seconds. The order of the conditions tested was randomized for each individual. Mean angular acceleration and standard deviation (degrees/second) of the three conditions were: (1) no hearing protection (control), 0.65 + 0.19, (2) CAEP, 0.69 + 0.23, and (3) QuietPro, 0.70 + 0.20 (one-way analysis of variance [ANOVA], df = 2, F = 0.38, p = 0.706). CONCLUSIONS: The components of an intact balance system include a variety of neural inputs, to include vesitbuloocular, vestibulospinal, and labyrinthine afferents. Both the CAEP and Nacre QuietPro are hearing preservation devices utilized during Operation Iraqi Freedom and Operation Enduring Freedom in Afghanistan. Our pilot data show no decrement in balance with utilization of these combat hearing preservation devices.

Using Auditory Steady-State Responses for Measuring Hearing Protector Attenuation.

INTRODUCTION: Present methods of measuring the attenuation of hearing protection devices (HPDs) have limitations. Objective measurements such as field microphone in real-ear do not assess bone-conducted sound. Psychophysical measurements such as real-ear attenuation at threshold (REAT) are biased due to the low frequency masking effects from test subjects' physiological noise and the variability of measurements based on subjective responses. An auditory steady-state responses (ASSRs) procedure is explored as a technique which might overcome these limitations. SUBJECTS AND METHODS: Pure tone stimuli (500 and 1000 Hz), amplitude modulated at 40 Hz, are presented to 10 normal-hearing adults through headphones at three levels in 10 dB steps. Two conditions were assessed: unoccluded ear canal and occluded ear canal. ASSR amplitude data as a function of the stimulation level are linearized using least-square regressions. The "physiological attenuation" is then calculated as the average difference between the two measurements. The technical feasibility of measuring earplug attenuation is demonstrated for the group average attenuation across subjects. RESULTS: No significant statistical difference is found between the average REAT attenuation and the average ASSR-based attenuation. CONCLUSION: Feasibility is not yet demonstrated for individual subjects since differences between the estimates occurred for some subjects.