The Auditory Protection and Performance Division (APPD) conducts sensory research to protect, sustain, and extend the operational capabilities of our Army’s Warfighters by using applied medical and operational techniques to study auditory and vestibular function.

Specific Research Platforms

APPD utilizes state-of-the-art equipment to efficiently and effectively support the Warfighter. Laser-Doppler Vibrometers are used to measure the movement of the eardrum in relation to different sound waves, enabling a proper understanding of the functions of the middle and inner ear.

Additionally, reverberation and anechoic chambers are used for various tests and studies including sound localization. These rooms allow researchers to examine properties of sound with and without echo effects, develop standards for testing sound localizations, determine how hearing protection effects sound localization, and determine speech intelligibility in degraded listening environments and other projects. Sound localization plays an important role in situational awareness and is essential to 3-dimensional (3-D) cuing, particularly when visual cuing is unavailable. The ability to take full advantage of auditory cues may improve situational awareness by providing orientation in degraded visual environments through critical auditory information not detected by other sensory organs.

APPD has the capability to perform Real Ear Attenuation at Threshold (REAT) tests at the Laboratory, allowing researchers to validate and verify the amount of protection that is provided by various hearing protectors under a variety of conditions. The laboratory also employs six and eight-inch shock tubes to test the effects of high impulse sound waves on headsets and other hearing protection devices. The tubes can be used to create a wide range of impulses that exceed 170 dB and replicate the effects of an explosion.

With the introduction of 3-D printing, APPD is working to print custom earplugs at the Laboratory. Traditionally, an impression of the ear would be shipped to a company, fabricated, and reshipped to the customer within a couple weeks. By investigating the efficacy of scanning the ear canal and fabricating custom earplugs locally, APPD may reduce the wait time for the customer and potentially expand hearing protection options for the Warfighter.

The NeuroKinetics, Inc.–I-Portal® Neurotologic Test Center rotary chair and Natus SMART EquiTest® CRS balance platform are used to assess the vestibular system. Both systems are being used to normalize vestibular data for aviators, pre- and post-deployment function, and pre- and post-injury function. These systems may be instrumental in determining standards concerning balance and spatial orientation, and may be used to evaluate fitness-for-duty in future periodic health assessments.

APPD Platforms - Graphic

Results
Research on blast overpressure and impulse noise from weapons contributed to acoustic safety standards for human exposure and directly resulted in the free-field exception to MIL-STD-1474D “Noise Limits.”

The Communications Earplug (CEP) is a device worn in combination with the aviator’s helmet that provides the exceptional hearing protection of an expanding foam earplug while passing to the ear the clearest speech signal attainable. This system was developed by APPD researchers who sought to provide sound attenuation and speech intelligibility to all Army rotary-wing aviators and crew without compromising operational effectiveness.


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