High Channel Count, High Density Microphone Arrays for Wind Tunnel Environments

The Interdisciplinary Consulting Corporation (IC2) proposes the development of high channel count, high density, reduced cost per channel, directional microphone arrays for noise source measurement using microelectromechanical systems (MEMS) based piezoelectric microphones with backside contacts and advanced packaging technology. The goal of this research is to develop an advanced phased-array technology to revolutionize array measurement capabilities through increases in array density and channel count while easing installation into wind-tunnels and significantly reducing cost per channel. Specifically, this array technology will be developed to address NASA needs for acoustic and relevant flow field measurement methods for subsonic, transonic and supersonic vehicles targeted specifically at airframe noise sources and the noise sources due to the aerodynamic and acoustic interaction of airframe and engines, as per Subtopic A1.02 Quiet Performance - Airframe Noise Reduction of the NASA FY 2017 SBIR/STTR Solicitation. This work is aimed at meeting the aerospace industrys need for economically viable array technology that meets required metrics. The focus of this project is to combine proven MEMS design principles and established device structures to develop high channel count, high-density acoustic arrays. The end results of this innovative approach are higher density acoustic arrays, with significantly-reduced cost per channel enabling higher channel arrays comprised of high bandwidth, high dynamic range, flush-mounted aeroacoustic microphones. Further, the thin form factor of the resulting array eases installation constraints and placement restrictions.

The proposed instrumentation technology has the potential to be transportable across multiple NASA facility classes as well as implemented across government-owned test facilities. The target application for entry into NASA ATP is as wind tunnel instrumentation for phase-array beamforming to enable noise source localization. In addition to wind-tunnel testing, the proposed microphone technology is also applicable to the types of technological solutions sought for pressure measurements and focusing acoustic measurements that can be used a flight-test tunnel environment and ground test instrumentation for static engine testing. The proposed innovation is applicable to NASA Langleys Subsonic Wind Tunnel for advanced phased array measurements of fixed- and rotary-wing civil and military aircraft, the Acoustics Research Laboratory's 20 x 24 x 30 anechoic quiet-flow facility, as well as LaRC's Aeroacoustics Branch by supplying validation of simulation of the Rotorcraft, the Subsonic Fixed Wing, and the Supersonic Projects. Additionally,it is useful for multiple NASA GRC facilities in the Acoustics Branch, the Aero-Acoustics Propulsion Laboratory, Small Hot Jet Acoustic Rig, Nozzle Acoustic Test Rig, and Advanced Noise Control Fan Rig. At NASA Ames, the technology benefits the Experimental Aerophysics Branch, and facilities such as the 7-by 10-Foot Wind Tunnel.

The proposed instrumentation technology has the potential to be implemented across government, industry and academic institution test facilities. The target market is instrumentation and measurement microphones and arrays for the aerospace industry. The target application is as wind tunnel instrumentation for phased-array beamforming to enable noise source localization. In addition to wind-tunnel testing, the proposed microphone technology is also applicable to the types of technological solutions sought for pressure measurements and focusing acoustic measurements that can be used in a flight-test tunnel environment and ground test instrumentation for static engine testing. The primary characteristic of this market is the need for high performance measurements with relatively low volume requirements. Ultimately, the cost per unit and size constraints of existing technologies limit the array size and density below customer desired levels. IC2 seeks to change that dynamic via microphones with reduced size and complexity, at drastically lower cost (roughly an order of magnitude), enabling vastly larger, affordable arrays of higher density. We achieve those goals while meeting individual microphone performance requirements,leading to potentially game-changing improvements in array performance. Potential commercial customers include industry aircraft manufacturers, such as Boeing, Northrop Grumman, Lockheed Martin, Gulfstream, Bombardier, and the academic research community.

This is early/mid-stage (TRL 6) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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