Piezoelectric MEMS Microphones for Ground Testing of Aeronautical Systems

Improving the acoustical environment is critical in aeronautics. Airports and aeronautical systems manufacturers are facing ever-increasing demands to reduce noise levels. Aeronautical applications require the use of large arrays of high quality microphones with a large dynamic range. These arrays are expensive. The advent of lower cost microphones that meet the users' specifications would dramatically improve the ability of engineers seeking to quantify the acoustic impact of either their designs or their facilities (e.g., airports) to make data driven decisions to improve any adverse conditions. We seek to develop commercially viable, piezeoelectric micro-electro-mechanical systems (MEMS) microphones capable of withstanding the high amplitude sound pressure levels and adverse environmental conditions found in ground testing of the acoustics of aeronautical systems. The acoustical specifications of these microphones (measured by noise floor, linearity, sensitivity) will met or exceed those of existing microphones. Our microphone is a shift from the capacitive sensing scheme that is used in nearly every microphone in use today. Piezoelectric MEMS microphones have significant advantages, over an above their small size (<4 mm x mm). Piezoelectric MEMS microphones require no polarization (unlike capacitive sensors), a significant price advantage when considering implementation in large arrays. In addition, the piezoelectric MEMS microphones can withstand the higher temperatures needed for lead-free re-flow soldering a significant advantage over electrets (that cannot withstand these high temperatures). This microphone, therefore, holds the promise of superior acoustical performance, lower cost than current technology, ease of implementation into large arrays, and seamless integration into modern microelectronics manufacturing procedures.

More than 2 billion microphones are sold each year. A piezoelectric MEMS microphone can address the needs of the vast majority of this market but will need to be designed appropriately for each sector of the market. This market can be broken up into roughly three categories. About half of the market, 1 billion units per year, is for extremely inexpensive microphones for toys and other applications where size and performance are not crucial. Roughly 1 billion units per year are also sold for consumer electronics, mostly for mobile phone applications. There is also a small market of high-end microphones for instrumentation, recording studios and live events. Examples of large arrays of instrument quality microphones used in the aerospace industry include the wind tunnel measurements (where over 1000 microphone could be used) and in the ground test arrays (like the Boeing QTD2 array with over 600 microphones). The overall instrumentation microphone market is estimated at 100,000 units per year with prices around $1500 to $3000 per microphone. This instrumentation market will be the initial target of the microphones fabricated by Baker-Calling. Other applications include: hearing aids and noise cancelling headsets.

There are a great number of NASA test facilities where lower cost microphones are needed that can withstand harsh environmental conditions and acoustic loading. A partial listing includes: 1. Glenn Research Center: Acoustic Test Lab: phased array systems (e.g., 16 element linear array, 80 element microphone cage array, 63 element microphone spiral array); Nozzle Acoustic Test Rig; AeroAcoustic Propulsion Lab; Advanced Noise Control Fan Rig. 2. Langley Research Center: Structural Acoustics Loads and Transmission facility; Jet Noise Lab; Mobile Acoustics Research Capability; Anechoic Noise Facility. 3. Noise mapping at airports using large arrays. The applications of noise control are to aircraft noise mitigation (jet engine noise, flow noise and structural acoustic radiation) as well as for understanding the acoustics surrounding airports.

This is a mature technology (TRL 7) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

None of these are guaranteed paths for this specific project — TechPort itself doesn't have an "apply" button. Reaching out to the contact(s) above with a specific question is usually the fastest way to find out what's actually open.