The Ultimate Directional MEMS Microphone
Physical Sciences : Mechanical
Available for licensing
- Neal Hall, Ph.D. , Electrical and Computer Engineering
- Michael Kuntzman, Ph.D. , Knowles Corporation
- Donghwan Kim , ME
- Karen Kirk , Mechanical Engineering
- Nishshanka Hewa-Kasakarage , ECE
Directional microphones employ innovative designs to sense sound with high sensitivity in preferred directions, while being insensitive to sound in other directions. Directional microphones are used in hearing aids, for example, to avoid the common "cocktail party" problem. Directivity enables a hearing aid wearer to listen to a speaker of interest with high sensitivity, while rejecting ambient background noise that would otherwise degrade speech intelligibility.
Clearly, directional microphones have potential to greatly improve speech intelligibility and signal clarity for a wide suite of consumer electronic devices, given the pervasive use of audio in our daily lives (e.g., smartphones, laptop computers, Bluetooth earpieces, hearing aid devices, etc.). Today, however, there is no commercially viable directional MEMS microphone technology.
Inventors at The University of Texas at Austin have developed a design that employs innovative mechanical properties plus low power piezoelectric readout to realize a pressure gradient sensor. It is possible to combine several gradient sensors on a single chip to sense gradients in all three axes.
- Design enables a drop-in replacement for current omnidirectional MEMS microphones used in common devices.
- Demonstrated performance reduces ambient noise compared to current designs.
- When multiple-direction microphones are combined with digital signal processing, advanced modalities are enabled.
Bulk and surface micro-machining techniques are employed to realize structures that mechanically respond to sound preferentially in certain directions while resisting a motional response to sound arriving in other directions. With directivity built into the mechanical structure, no electronics are required to implement directivity and the sensor does not suffer from phase matching issues, as is the case with omnidirectional microphone pairs configured for a directional response.
Since their entry into the market, electrostatic MEMS microphones have become one of the highest growth areas for MEMS, growing from less than 300 million units shipped in 2007 to over 1 billion units shipped in 2011. Today many major semiconductor companies manufacture and sell electrostatic MEMS microphones, including Knowles Electronics, Analog Devices, Infineon, and ST Mircoelectronics. The top four end users of MEMS microphones are Apple, Samsung, LG, and Motorola Mobility. Apple’s iPhone 4, for example, contains three separate electrostatic MEMS microphones—two in the body of the phone and a third in the mobile headset.
- 1 U.S. patent application filed
- 1 U.S. patent issued: 9,372,111