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Low Power Tri-axial Acoustic Sensor


The U.S. Customs and Border Protection (CBP) use UGS units to detect personnel, vehicles, and aircraft engaged in illegal activity at the U.S. border. The UGS units consist of: sensor(s) for detecting activity; a buried housing that contains a processing unit that interprets the received signals from the sensor(s) and performs administrative and control tasks; a radio for communicating alarms back to a CBP Command Center; and a power supply. An UGS unit normally employs a microphone to detect acoustic energy generated by the target. Processing of the received acoustic signal can provide information on the time the target passed the UGS, and the targets’s speed and range. Line-of-bearing and track information in near real time is desirable for the Border Patrol (BP) to determine where a target engaged in illegal activity may be headed. With the current deployment of single channel microphone UGS units, tracking information would have to be realized from the use of multiple UGS units and correlation of the individual information from them. Deploying multiple UGS units entails an operational impact and it is desirable to be able to develop a track solution from a single UGS.

A low cost, low power, acoustic sensor that can provide directional information in both heading and altitude (for aircraft) and which can be integrated with existing UGS units is desired. It should be noted that the acoustic signature of some types of targets is narrowband in nature such that correlation processing of multiple acoustic sensors at the UGS site is not deemed viable (i.e., Army’s Boomerang sensor unit). A tri-axial acoustic sensor would provide the desired functionality for operating near the border. In order for a tri-axial acoustic sensor to be reasonable for employment, the cost of the sensor can’t greatly increase the overall cost of a deployed UGS units. Commercially available UGS units may range in cost from $2K-$10K depending upon the vendor. A tri-axial acoustic sensor also should not increase the power consumption of the UGS markedly either. Sensor power consumption should be on the order of three times that of a microphone sensor (ignoring increased processing requirements) when all three channels are used. The bandwidth of the directional acoustic sensor should be great enough to capture the acoustic signature of the different types of targets.

Directional acoustic sensors proposed for this solicitation need to show that their sensitivity or self noise does not markedly decrease the detection range of a target in comparison to a single channel microphone. Directional acoustic sensors proposed for this solicitation also need to address the sensitivity of the sensor to wind noise and/or the ability to shield the sensor from wind noise. Directional acoustic sensors proposed for this solicitation also will require an alignment capability or an alignment procedure such that heading measurements can be related to absolute coordinates. It should be noted that UGS are often deployed at night in a covert fashion and an alignment process that compromises the covertness of the deployment would not be acceptable.

PHASE I: Provide detailed analysis on sensitivity, self noise, wind noise abatement, directional capability, power, packaging, alignment, and cost for the proposed sensor. Consider/analyze methods for reducing power consumption (i.e., initially detecting and classifying a target on a single axis and using multiple axes only for tracking). Verify the analysis with measured data obtained both from laboratory testing and from field testing.

PHASE II: Work with an UGS manufacturer (approved by DHS S&T) for interfacing the directional acoustic sensor to their UGS units. The interface will involve both hardware and software modifications that will need to be performed by the UGS manufacturer. Laboratory test the prototype unit for self noise, directional accuracy, power draw, overall UGS power change from a single channel microphone configuration, and alignment accuracy. Field test the prototype unit with the directional acoustic sensor against targets of interest and verify detection range and tracking capability.

PHASE III: COMMERCIAL APPLICATIONS: Refine sensor packaging from the Phase II field trials. Market and transition the directional sensor capability to UGS vendors used by DHS and also UGS vendors used by the U.S. Army and Marine Corps.

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