Natural Hearing Restoration for Encapsulating Helmets
SBIR FY03.2 Topic A03-043
Department of Defense (DoD)/ARMY - Army Research Lab (ARL)

The entire solicitation may be viewed at

A03-043 TITLE: Natural Hearing Restoration for Encapsulating Helmets


OBJECTIVES: Develop a system that will restore natural hearing to a soldier wearing a fully encapsulating helmet.

DESCRIPTION: Current designs for future Army's helmets, e.g., the Objective Force Warrior (OFW) helmet, focus on a fully encapsulating helmet integrated into the war fighter ensemble. It has been historically shown that soldiers performing tasks that require listening for auditory queues will doff their helmet so they can use their own natural hearing to its fullest capability. Directional information about the dynamically changing acoustic environment is critical to their mission execution and force protection. Encapsulation of the soldier's head will greatly reduce their situational awareness and thus their ability to complete their mission. The hearing restoration system can be integrated into or developed as a part of an encapsulating helmet. A soldier wearing this system would perceive the acoustic environment around himself or herself as if they were hearing it without a helmet. The system is intended to restore natural listening ability of the soldier wearing an encapsulating helmet without affecting the ballistic or Nuclear Biological and Chemical (NBC) protection provided by the helmet.

Restoration of natural hearing can be accomplished by physical design or electrical means. Special molded forms or microphones or microphone arrays can be used to capture the surrounding acoustic environment. The sounds from these systems can be further processed or filtered to restore the effects of the soldier's head and torso on the received natural sounds. The particular avenue for development of the acoustically transparent helmet is left up to the contractor. Additional capabilities of the system such as noise reduction and selective signal filtering should be considered if feasible.

Along with development of the system, the contractor will also devise a test to measure the attenuation, speech intelligibility, and signal localization of their system in realistic noise conditions. The test data should include bare head and un-restored encapsulating helmet measurements for comparison. The contractor may perform these tests in-house or use government furnished equipment and expertise.

PHASE I: Develop and provide a working concept demonstration of natural hearing restoration. The demonstration can use proprietary or commercial off the shelf (CoTS) devices. Deliverables shall include a written report that includes the expected values of signal loss (attenuation), speech recognition and sound localization of the proposed system as compared with bare head measurements. As a minimum, the proposed design should provide significant performance improvement over the un-restored encapsulating helmet with the bare head measurements being the goal.

PHASE II: Develop and demonstrate a cost effective prototype system that incorporates the findings from phase I into an encapsulating helmet. The government can provide the encapsulating helmet if so required. Deliverables at the end of this phase will include the prototype system and technical documentation describing the system and providing operational data.

PHASE III: Integrate the prototype system into the current OFW encapsulating helmet. This phase will include utilizing mil spec components, ruggedizing any of the hardware, and miniaturizing the system. Devise and execute testing procedures to evaluate the subjective and objective measures of the system including attenuation of the restored sounds, helmet attenuation of natural sounds, speech recognition, and degrees of accuracy of signal localization in azimuth and elevation.

DUAL USE APPLICATIONS: There is a current need in military and civilian applications for the development of a system that restores natural hearing in an encapsulating helmet. The OFW has a current specification for an encapsulating helmet. This system can also be used for civilian operations such as HASMAT operations and search and rescue where the operators are wearing head encapsulating gear.


[1] Shinn-Cunningham, B. G., Lehnert, H., Kramer, G., Wenzel, E. M., and Durlach, N. I. (1997) Auditory Displays. In R. Gilkey and T. Anderson (Eds.), Binaural and Spatial Hearing in Real and Virtual Environments. Mahwah, NJ: Lawrence Erlbaum, pp. 611-664.

[2] Durlach, N. I., and Wenzel, E.M. (1994) Auditory displays. In Durlach, N. I. and Mavor, A. S. (Eds.) Virtual Reality: Scientific and Technological Challenges. Report of the Committee on Virtual Reality Research and Development. Washington, DC: National Academy Press.

[3] Durlach, N. I. (2003) Supernormal Listening Systems, accessed at

[4] Vause, N.L., and Grantham, D. W. (1999) Effects of Earplugs and Protective Headgear on Auditory Localization Ability in the horizontal Plane, Human Factors 41(2), 282-294.

KEYWORDS: Natural Hearing, Encapsulating Helmet, Sound Localization

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