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Advanced, compact acoustic particle velocity-pressure sensory system

Description:

TECHNOLOGY AREA(S): Electronics 

OBJECTIVE: Develop an advanced acoustic particle velocity-pressure sensory system that is compact, ruggedized, and modular for anticipated missions involving acoustic localization, signal intelligence and other uses. 

DESCRIPTION: The U.S. Army is seeking research and development in acoustic particle velocity and acoustic pressure sensing technologies that can be implemented for use in acoustic signal detection, localization, tracking, and characterization. The technologies must be highly modular and capable of integration into atmospheric acoustic detection systems both current and future. Technologies focusing on modular design are highly desired. An environmentally self-aware system is envisioned. Current microphone array systems are used to detect, localize, and classify acoustic sources. Dependent upon the source and range of interest, these systems have large foot prints, ranging from several to tens of square meters. The Army seeks reduced Size, Weight, and Power (SWaP) systems. Systems that not only reduce the array system footprint, but also reduce power are highly desired. Versatility of usage is important, as sources of interest may be harmonic or impulsive, transient or continuous. Systems may be deployed in a variety of outdoor environments, to include, urban, desert, mountainous, and littoral. Ruggedized systems that can withstand environmental extremes are a necessity for outdoor emplacement. Systems may be land-based or airborne, on the move or stationary. 

PHASE I: The company will define and develop a concept for a compact acoustic particle velocity (three-dimensional)-pressure sensory system (APV-P) with modularity to include environmental state measurements (APV-P/E) that meets the requirements as stated in the topic description. The company will demonstrate the feasibility of the concept in meeting Army needs and will establish that the concept can be developed into a useful product. Material testing and analytical modeling will establish feasibility. The concept development effort should assess the importance of several acoustic sensing factors for the APV-P, such as dynamic range, wind noise mitigation, signal fidelity, preservation of waveform, sampling rates, well-defined calibration, and ease of calibration. Evidence of design optimization of these parameters, as well as a comparison between model predictions and measured performance are required. Modularity of the acoustic-environmental APV-P/E system, to include integrating meteorological sensors, should be established. Environmental parameters to be measured include wind velocity (speed and direction), humidity, temperature, and atmospheric pressure. Plans for implementing the APV-P will be included as an output of Phase I, along with estimated performance. The APV-P will be designed to operate at frequencies between 0.1 Hz to 10 kHz, but demonstration below 0.1 Hz is also desired. The minimum dynamic range of the APV-P should be -10 dB to 150 dB, though a larger range, on both sides, is desired. Methods to manage different sound levels should be considered, such as adjustable gains. Data acquisition should have a minimum sampling rate of 25 kHz, with a minimum of 24-bit resolution. Sensitivity of the particle velocity detection should be established to correspond with the sensitivity of the pressure sensing. Of particular concern is calibration of the system; methods for in-field, self-calibration are desired. Operational conditions also should be considered, the APV-P/E system should fully function between -30 to 70 degrees Celsius, though a larger performance range is desired. A ruggedized system is required, being able to operate in severe environments, including rain and fine-particulate environments. Environmental parameter sampling should provide for atmospheric (thermal-mechanical) turbulence characterization at the acoustic scales. 

PHASE II: Based on the results of Phase I, the company will develop a prototype APV-P/E for evaluation. The prototype will be evaluated to determine the capability in meeting performance goals and Army requirements. System performance will be demonstrated through prototype evaluation and modeling or analytical methods over the required range of parameters. Evaluation results will be used to refine the prototype into a design that will meet Army requirements. The APV-P system should include wind noise mitigation. Documentation should include analyses comparing system response to scientific grade microphones, performance for harmonic and impulsive sources, direction finding compared to conventional systems (including azimuth, elevation, and ranging sensitivity), assessment of wind noise mitigation, and preservation of acoustic waveform. 

PHASE III: The company will support the Army in transitioning the technology for Army field use. The company will develop an APV-P/E system according to the Phase III development plan for evaluation to determine its effectiveness in an operationally relevant environment. The company will support the Army for test and validation to certify and qualify the system for Army use and transition the APV-P/E to its intended platform. The envisioned military applications of the APV-P/E system include: detection, localization, tracking, and classification of a variety of sources, to include sniper and small-arms fire, rocket launches, explosions, and ground and airborne vehicles; characterization of atmospheric turbulence; and studies of acoustic wavefronts. A compact design is envisioned, allowing emplacement on ground and air vehicles. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The APV-P/E system has commercial applications that include gunshot detection and localization, aircraft/unmanned aircraft vehicles localization and tracking, intruder detection, environmental hazard assessments (e.g., volcanic and tornadic activity), and acoustic tomography of the atmosphere. The commercial market is typically quick to adopt technology that enhances performance while controlling cost and reducing SWaP. The company is expected to pursue civilian applications and additional commercialization opportunities. 

REFERENCES: 

1: L Solomon, L Sim, and J Wind, "Analysis of MEMS-based Acoustic Particle Velocity Sensor for Transient Localization," U.S. Army Research Laboratory Technical Report, ARL-TR-5686 (2011).

2:  SL Collier, et al, "Atmospheric turbulence effects on acoustic vector sensing," Proc. Meet. Acoust. 30, 045009 (2018).

3:  DC Swanson, Signal Processing for Intelligent Sensor Systems (Taylor & Francis, 2000).

4:  K Attenborough, KM Li, and K Horoshenkov, Predicting Outdoor Sound (CRC Press, 2006).

5:  R Raspet, et al, "New Systems for Wind Noise Reduction for Infrasonic Measurements," in Infrasound Monitoring for Atmospheric Studies: Challenges in Middle-atmosphere Dynamics and Societal Benefits. Second Edition. (Editors: A Le Pichon, E Blanc, A Hauchercorne

6:  Springer International Publishing, 2018).

KEYWORDS: Acoustic Pressure, Acoustic Particle Velocity, Microphone, Acoustic Vector Sensor, Self-aware Sensor 

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