Microelectromechanical Systems Microphone Research Articles

Capacitive MEMS microphones

More than two billion microphones are produced annually. The electret microphone, invented by Sessler and West in the early 1960s, makes up the bulk of this production. With the desire for more functionality as well as smaller size, microelectromechanical systems (MEMS) microphones are now being proposed to become the microphone of choice for consumer audio applications. There are two major application areas that are driving the interest in MEMS microphones: hearing aids, where size and integration with digital signal processing are important, and consumer devices, where there is interest in reducing costs by integrating a complete systems solution on an integrated circuit. This paper describes some fundamental MEMS microphone design issues. An all-surface machined MEMS microphone that was built at Bell Labs is also described.

Design and fabrication of 128-channel MEMS-based acoustic array

Surface-mount microphones based on MEMS (micro-electromechanical system) technologies have recently become viable as component-level engineering solutions for acoustic measurements. In addition, advances in microelectronics, flexible circuitry, and array processing have motivated the design of a high-speed, low-cost acoustic array system for aeroacoustic measurements. A variety of microphones are available in the market today. Each type of microphone has its benefits and drawbacks. For example, standard condenser microphones have excellent sensitivity, stability, and high frequency response, but tend to be unwieldy, expensive, and require relatively high operational voltages. Electret microphones are small and fairly inexpensive but their performance deteriorates if exposed to moderately elevated temperatures. MEMS microphones combine the best features of the electret and condenser microphones while occupying a volume of less than 20 cubic millimeters. This paper details the custom-made 128-channel MEMS-based acoustic array for wind tunnel applications as well as the electrical, mechanical, and acoustic properties of the MEMS microphones utilized here.

A Comparative Study of Sound Localization Algorithms for Energy Aware Sensor Network Nodes

Sound localization using energy-aware hardware for sensor networks nodes is a problem with many applications in surveillance and security. In this paper, we evaluate four algorithms for sound localization using signals recorded in a natural environment with an array of commercial off-the-shelf microelectromechanical systems microphones and a specially designed compact acoustic enclosure. We evaluate performance of the algorithms and their hardware complexity which relates directly to energy consumption.

Scaling issues in a submillimeter MEMS microphone

A silicon based microphone with a 0.5 mm diam diaphragm has been developed using a combination of surface and bulk micromachining or MicroElectro Mechanical Systems (MEMS) techniques. This device is intended for high volume general purpose markets such as telephony, where cost is a key factor. In batch fabricated MEMS devices, cost is critically determined by the device size. Yet the performance standards for this microphone are set by relatively large electret condenser microphones (ECM) built in competing technologies. This paper will discuss the scaling issues involved in meeting high performance goals in a very small MEMS device. In particular, tradeoffs made to achieve high sensitivity, low noise, and unconditional stability will be discussed.