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Cambridge, MA, United States

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 64.13K | Year: 1995


Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase I | Award Amount: 99.86K | Year: 2008

Acoustic cloaking – the ability to direct sound completely around an object – is an exciting possibility. Potential military applications include making underwater objects invisible to threat sonar and creating quiet zones where, for example, otherwise noisy manned underwater operations can be safely carried out or where battlefield noise can be contained. Commercial applications are almost limitless. Metamaterials have been well described in the literature and some electromagnetic prototypes have been demonstrated. The key to making an acoustic metamaterial is anisotropy of its effective material properties. Very recently, designs for underwater spherical and cylindrical cloaks have been developed requiring that the effective density of a material be described as a tensor, that is, that it have two different values depending on direction. In this proposed project, a means to construct metamaterials with this property using very simple, inexpensive and rugged dynamical elements commonly used for vibration reduction will be demonstrated. A promising naval application will be identified and a suitable metamaterial and cloak geometry will be designed for it. A test model representative of the metamaterial will be built and tested in air as a proof of principle. This model will be tested in water in the Phase I option.

Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase II | Award Amount: 412.59K | Year: 2008

This proposal is concerned with two important aspects of sound as it affects divers; the ability to receive and send communications (“comms”), and the effects of ambient noise, particularly in construction and demolition activity. SCUBA divers wear a breathing apparatus and their ears are often flooded so that systems that occlude the ear canal that are satisfactory at sea level pose a danger as the ambient pressure changes. Helmeted divers have “dry” ear canals but the issue of changing pressurization remains. Pilots and flight deck personnel are being supplied with active noise reduction (ANR) systems that provide both noise reduction and comms that use both muffs and in-the-ear-canal speakers. This proposed effort is focusing on how the two needs for hearing protection and communications can be achieved for both SCUBA and helmeted divers. The work relies heavily on our Phase I effort on underwater communications and concurrent work on an ANR system for Air Force and Navy flight deck personnel, both of which make use of single crystal relaxor ferroelectric (lead magnesium niobate - lead titanate) materials to generate sound. Different types of transducers, their layout, and the electronic design are being considered to achieve both ANR and communications goals.

Agency: Department of Defense | Branch: | Program: STTR | Phase: Phase II | Award Amount: 749.87K | Year: 2006

Knowing the kind(s) of machinery and equipment contained in a building and its approximate location prior to having to enter the building is a valuable asset to military operations, particularly in urban situations. The proposed system, called BIMLI (Bui

Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase I | Award Amount: 99.90K | Year: 2007

This proposal is concerned with the use of single crystal PMN-PT as a transducer element in underwater communication systems. The high sensitivity and strain capability of these materials makes them unusually appropriate for the demands of small size and high output needed in this application. Developments already underway as an element in active noise reduction earplugs for personnel on the flight decks of aircraft carriers lead naturally to the use of similar transducers for in-the-ear loudspeakers for personnel carrying out underwater missions, particularly in the littoral ocean zones. Such activities are of particular value in communicating with personnel who will wear ear canal insert earphones resistant to water and pressure, and still maintain a high degree of fidelity, frequency and dynamic range for the presentation of transmitted messages. The same or similar elements can also serve as microphones or hydrophones as part of a two-way communications link. The progress and experience we already have in working with PMN-PT has convinced us of the special advantages that this material has when incorporated into small, high output acoustical drivers, and offers an unusual opportunity to design and prototype a transducer for underwater communications.

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