Effects of unilateral eye closure on middle ear muscle contractions.

Middle ear muscle contractions (MEMCs) are most commonly considered a response to high-level acoustic stimuli. However, MEMCs have also been observed in the absence of sound, either as a response to somatosensory stimulation or in concert with other motor activity. The relationship between MEMCs and non-acoustic sources is unclear.

Generalizability of clinically measured acoustic reflexes to brief sounds.

Middle ear muscle contractions (MEMC) can be elicited in response to high-level sounds, and have been used clinically as acoustic reflexes (ARs) during evaluations of auditory system integrity. The results of clinical AR evaluations do not necessarily generalize to different signal types or durations. The purpose of this study was to evaluate the likelihood of observing MEMC in response to brief sound stimuli (tones, recorded gunshots, noise) in adult participants (N = 190) exhibiting clinical ARs and excellent hearing sensitivity.

Human middle-ear muscles rarely contract in anticipation of acoustic impulses: Implications for hearing risk assessments.

The current study addressed the existence of an anticipatory middle-ear muscle contraction (MEMC) as a protective mechanism found in recent damage-risk criteria for impulse noise exposure. Specifically, the experiments reported here tested instances when an exposed individual was aware of and could anticipate the arrival of an acoustic impulse. In order to detect MEMCs in human subjects, a laser-Doppler vibrometer (LDV) was used to measure tympanic membrane (TM) motion in response to a probe tone.

Acoustic reflexes are common but not pervasive: evidence using a diagnostic middle ear analyser.

Objective: The objective of this study is to determine whether acoustic reflexes are pervasive (i.e. known with 95% confidence to be observed in at least 95% of people) by examining the frequency of occurrence using a friction-fit diagnostic middle ear analyser.

Acoustic reflexes are common but not pervasive: evidence from the National Health and Nutrition Examination Survey, 1999-2012.

Objective: To determine whether acoustic reflexes are pervasive (i.e. sufficiently prevalent to provide 95% confidence of at least 95% prevalence) and might be invoked in damage-risk criteria (DRC) and health hazard assessments (HHA) for impulsive noise.

Inter-laboratory comparison of three earplug fit-test systems.

The National Institute for Occupational Safety and Health (NIOSH) sponsored tests of three earplug fit-test systems (NIOSH HPD Well-Fit, Michael & Associates FitCheck, and Honeywell Safety Products VeriPRO). Each system was compared to laboratory-based real-ear attenuation at threshold (REAT) measurements in a sound field according to ANSI/ASA S12.6-2008 at the NIOSH, Honeywell Safety Products, and Michael & Associates testing laboratories.

Effects of repetitive low-level blast exposure on visual system and ocular structures.

Unlabelled: The purpose of this study was to determine whether repetitive exposure to low-level blasts during military breacher training produces acute and cumulative damage to the ocular tissues or visual system. The effects of low-level blast exposure on high-contrast visual acuity, contrast sensitivity, oculomotor function, color vision, visual field (VF), pupillary light reflex, corneal endothelial cell density (ECD), macular thickness, retinal nerve fiber layer thickness, and cup-to-disc ratio were assessed using a battery of standard clinical ophthalmic tests administered 10 times over a 2-year period. Data from nine breacher instructors (Cadre) were compared with data from four breacher engineers (CONTROL).

Analysis of army-wide hearing conservation database for hearing profiles related to crew-served and individual weapon systems.

Damage-risk criteria (DRC) for noise exposures are designed to protect 95% of the exposed populations from hearing injuries caused by those noise exposures. The current DRC used by the US military follows OSHA guidelines for continuous noise. The current military DRC for impulse exposures follows the recommendations from the National Academy of Sciences--National Research Council Committee on Hearing, Bioacoustics, and Biomechanics (CHABA) and are contained in the current military standard, MIL-STD-1474D "Noise Limits.

Results of the National Institute for Occupational Safety and Health-U.S. Environmental Protection Agency interlaboratory comparison of American National Standards Institute S12.6-1997 Methods A and B.

The National Institute for Occupational Safety and Health and the Environmental Protection Agency sponsored the completion of an interlaboratory study to compare two fitting protocols specified by ANSI S12.6-1997 (R2002) [(2002). American National Standard Methods for the Measuring Real-Ear Attenuation of Hearing Protectors, American National Standards Institute, New York].

A field investigation of hearing protection and hearing enhancement in one device: for soldiers whose ears and lives depend upon it.

Operational hearing protection and maintenance of audibility of signals and speech are considered force multipliers in military operations, increasing Soldier survivability and lethality. The in-field research described in this paper was conducted to examine operational performance effects of three different hearing enhancement protection systems (HEPS) that are intended to provide both protection and audibility. The experiment utilized operationally-defined measures in full-scale, simulated combat scenarios with Army ROTC Cadet Soldiers as subjects.

Speech intelligibility in noise using throat and acoustic microphones.

Introduction: Helicopter cockpits are very noisy and this noise must be reduced for effective communication. The standard U.S.

Relations among early postexposure noise-induced threshold shifts and permanent threshold shifts in the chinchilla.

Threshold shifts (TS) were measured at various times following a wide variety of noise exposures on over 900 chinchillas. An analysis of postexposure TS measures and noise-induced permanent threshold shift (PTS) showed that, across audiometric test frequency, there was a consistent relation between these variables of the form PTS (dB) = alpha(e(TS/beta) - 1), where, for a given test frequency, alpha (dB) and beta (dB) are constants. TSs were measured immediately following exposure (TS0), 24 h after exposure (TS24), and at several intermediate times in order to estimate the maximum TS (TSmax).