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We report evidence for nonlinear modes in the ringdown stage of the gravitational waveform produced by the merger of two comparable-mass black holes. We consider both the coalescence of black hole binaries in quasicircular orbits and high-energy, head-on black hole collisions. The presence of nonlinear modes in the numerical simulations confirms that general-relativistic nonlinearities are important and must be considered in gravitational-wave data analysis.

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Massive vector fields feature in several areas of particle physics, e.g., as carriers of weak interactions, dark matter candidates, or an effective description of photons in a plasma. Here, we investigate vector fields with self-interactions by replacing the mass term in the Proca equation with a general potential. We show that this seemingly benign modification inevitably introduces ghost instabilities of the same kind as those recently identified for vector-tensor theories of modified gravity (but in this simpler, minimally coupled theory). It has been suggested that nonperturbative dynamics may drive systems away from such instabilities. We demonstrate that this is not the case by evolving a self-interacting Proca field on a Kerr background, where it grows due to the superradiant instability. The system initially evolves as in the massive case, but instabilities are triggered in a finite time once the self-interaction becomes significant. These instabilities have implications for the formation of condensates of massive, self-interacting vector bosons, the possibility of spin-one bosenovae, vector dark matter models, and effective models for interacting photons in a plasma.

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Noise exposure is a known occupational health hazard to those serving in the military. Previous military epidemiology studies have identified military occupations at risk of noise induced hearing loss (NIHL); however, musicians have not been specifically mentioned. The focus of military NIHL studies is usually on those service members of the combat arms occupations. This project was a preliminary examination of Department of Defense (DoD) active duty military musicians in regard to their noise exposure, annual hearing test rates, and hearing injury rates using available data sources. The analysis concluded that DoD military musicians are an underserved population in terms of hearing conservation efforts. Noise surveillance data extracted from the Defense Occupational and Environmental Health Readiness System-Industrial Hygiene showed that every musician similar exposure group (SEG) with noise survey data from 2009 to 2013 exceeded the occupation exposure level adopted by DoD Instruction 6055.12. However, only a small percentage of all DoD active duty military musicians (5.5% in the peak year of 2012) were assigned to a SEG that was actually surveyed. Hearing test data based on Current Procedural Terminology coding extracted from the Military Health System revealed that the percentage of musicians with annual hearing tests increased over the 5 years studied in all services except the Air Force. During 2013, the data showed that the Navy had the highest percentage of musicians with annual hearing tests at 70.9%, and the Air Force had the lowest at 11.4%. The Air Force had the highest percentage of hearing injuries of those musicians with annual hearing tests for all 5 years analyzed. Although noise surveillance and annual hearing tests are being conducted, they occur at a much lower rate than required for a population that is known to be overexposed to noise.

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PURPOSE: To evaluate noise-induced hearing injury (NIHI) and blast-related comorbidities among U.S. Army soldiers in an effort to understand the morbidity burden and future health service requirements for wounded war fighters returning from the Central Command Area of Responsibility, predominantly from Iraq and Afghanistan deployments. METHOD: Inpatient and outpatient records with diagnosed NIHI or blast-related comorbidities (e.g., significant threshold shift [STS], noise-induced hearing loss, tinnitus, sensorineural hearing loss, eardrum perforations, mild traumatic brain injury, and posttraumatic stress disorder) were extracted for active duty soldiers returning from combat deployments. Records were limited to those within 6 months of the soldier's return date from April 2003 through June 2009. To account for changes in STS coding practice, STS rates observed after October 1, 2006, were used to extrapolate prior probable postdeployment STS. RESULTS: Statistically significant increases were observed for tinnitus, dizziness, eardrum perforations, and speech-language disorders. The combination of observed and extrapolated STS yielded a conservative estimate of 27,427 cases. CONCLUSIONS: Estimates can be used to forecast resource requirements for hearing services among veterans. This article could serve as a guide for resourcing and innovating prevention measures and treatment in this population. Data provided may also serve as a baseline for evaluating prevention measures.

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INTRODUCTION: Rates of noise-induced hearing injury (NIHI) among U.S. active duty military have not been previously described using available military medical surveillance data. METHODS: NIHI were identified in the Defense Medical Surveillance System (DMSS) using a list of ICD-9-CM diagnosis codes selected in collaboration with military audiologists. To provide a more comprehensive view of the NIHI problem, NIHI-related ICD-9 codes beyond the traditional 388 noise injury-code set were included. Visit rates by gender and age group are reported by quarter, 2003-2005. Overall frequencies and rates by occupational specialty, 2003-2005, are also described. RESULTS: From 2003 to 2005, rates for men were significantly higher than rates for women, with rate ratios (RR) ranging from 1.15 (95% CI =1.07, 1.23) to 1.78 (95% CI= 1.62, 1.93). Rates among women ranged from 2.9 to 6.2 per 1000 person-years; rates among men ranged from 4.5 to 6.7 per 1000 person-years. NIHI rates were highest among those aged > or =40 years and lowest among those aged 17-19 years, with RRs ranging from 3.06 (95% CI=2.77, 3.40) to 5.51 (95% CI=4.88, 6.30) during this time period. Among occupational groups, general officers/executives had the highest NIHI rate over this time period (29.5/1000 person-years), followed by enlisted personnel in training (14.3/1000 person-years) and scientists and professionals (12.8/1000 person-years). CONCLUSIONS: While data on outpatient injury causes and use of hearing protection are also needed to guide the future design and/or modification of interventions, existing military medical surveillance provides essential information for tracking NIHI and monitoring NIHI intervention effects.

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BACKGROUND: Hearing deficiency is the condition for which accession medical waivers are most commonly granted. The retention of individuals entering service with a waiver for hearing deficiency has not been previously studied. METHODS: Military retention among new enlistees with a medical waiver for hearing deficiency was compared with that among a matched comparison group of fully qualified enlistees. Comparisons according to branch of service over the first 3 years of service were performed with the Kaplan-Meier product-limit method and proportional-hazards model. RESULTS: Army subjects had significantly lower retention rates than did their fully qualified counterparts. In the adjusted model, Army and Navy enlistees with a waiver for hearing deficiency had a significantly lower likelihood of retention than did their matched counterparts. DISCUSSION: The increased likelihood of medical attrition in enlistees with a waiver for hearing loss provides no evidence to make the hearing accession standard more lenient and validates a selective hearing loss waiver policy.

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BACKGROUND: The Department of Defense Hearing Conservation Program requires that a reference audiogram be performed at initial entry training (IET), before noise exposure. In the Army, only Fort Sill, home of the field artillery, and Fort Benning, home of the infantry, are in compliance. All military applicants receive a screening audiogram at a military entrance processing station (MEPS) to qualify for service. This audiogram does not meet the Defense Occupational and Environmental Health Readiness System-Hearing Conservation (DOEHRS-HC) standard. Nevertheless, it has been proposed that the MEPS screen be used as the reference because of limited resources and time during IET medical in-processing. METHODS: A total of 11,816 individual reference audiograms performed at Fort Sill 95th Adjutant General Recruit Reception Center in 2000 were identified in the DOEHRS-HC database. Results of the MEPS screening audiograms were found for 11,311 (96%) of these individuals. The two audiograms were compared by frequency and ear and by using the two Department of Defense criteria for threshold shift. RESULTS: A total of 14.49% (95% confidence interval, 14.48-14.50%) of audiograms using the three-frequency average difference and 23.19% (95% confidence interval, 23.18-23.20%) using the four-frequency difference in either ear demonstrated a threshold shift. The mean difference in intensity between the two audiograms ranged from 5 to 12 dB and varied by frequency and ear, with the greatest differences being seen at 500 and 6,000 kHz and in the left ear, compared with the right ear. The mean threshold level was higher for each frequency in the DOEHRS-HC audiogram, compared with the MEPS audiogram. CONCLUSIONS: Approximately 15% of soldiers at Fort Sill in 2000 showed a clinically significant threshold difference between their MEPS screening and the DOEHRS-HC baseline audiogram. Methodological variations in testing and interval noise-induced hearing loss could account for these differences. The results do not support the use of the MEPS screening audiogram as the reference audiogram. Compliance with the Hearing Conservation Program in the Army would require either improving MEPS testing to DOEHRS-HC standards or performing baseline audiograms at all five IET sites.

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PURPOSE: U.S. Army soldiers face unique noise exposures in the current deployed setting. The effects of these deployment-related exposures have not previously been documented. METHOD: In an attempt to initiate this process, medical evaluations performed at military audiology clinics from April 2003 through March 2004 were reviewed to compare noise-induced hearing loss injury (NIHLI) outcomes among soldiers whose diagnoses were classified as postdeployment-related versus non-postdeployment-related. Sentinel NIHLI outcomes of interest included acoustic trauma, permanent threshold shift, eardrum perforation, tinnitus, and military-specific H-3 and H-4 hearing loss profiles. RESULTS: Significantly higher rates of NIHLI and associated outcomes were observed among soldiers whose diagnoses were postdeployment-related. CONCLUSIONS: Based on the findings from this evaluation, recommendations are provided for enhancing the force health protection posture for prevention of hearing loss in future deployments.

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The Joint Committee on Infant Hearing (JCIH, 2000) has presented principles and guidelines for universal newborn hearing screening and early hearing detection and intervention (EHDI). The guidelines describe the need for a national data set for early hearing detection and intervention. The guidelines fail to provide the specific constructs for such a data set. To the authors' knowledge, no nationally proposed uniform data structure exists to capture EHDI services' outcome metrics. This article presents a proposed newborn hearing screening and EHDI data model. This model was developed to record EHDI outcomes data from Military Health System birthing centers. The data are to be collected for tracking implementation of Healthy People 2010 goals related to newborn hearing screening and EHDI programs within the Military Health System. In this article, the authors use the T. Helfer, A. Shields, and K. Gates (2000) methods to model a uniform structure for collection of newborn hearing screening and EHDI data. They also discuss expansion of the data model for application to public health reporting of EHDI outcomes in the civilian sector to include integration of Census Bureau demographic data and geographic information system data to further enhance the research value of these EHDI outcomes data. They offer the data model with the intention of supporting national research efforts for studying the efficacy of EHDI programs and to help establish a national evidence-based practice database for such programs.

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