I'm told that MEMS microphones already account for about 20% of the cell phone market. The downside to the MEMS microphone is its cost--it's about 2X, as compared with an ECM microphone, which costs about 25 cents. Analog Devices happened to launch a family of MEMS microphones last month.

The biggest current market MEMS devices are crash sensors in automobiles. But they really hit the microphone scene in a big way with the introduction of Motorola's extremely popular RAZR phone. In that application, the mike was designed as a surface-mount device, one that could withstand high temperatures. Since that time, the industry is producing about 200 million MEMS-based microphones per year, compared with about 2 billion ECM microphones in the same time period.

The current MEMS microphone consists of two ICs in a package, the sensor and the pre-amp. Analog Devices, who continues to develop MEMS-based microphones, believes it won't be long before further integration occurs. This includes a model with a digital output.

The tradeoff between the microphones is that the MEMS mikes can withstand higher temperatures, but they're more expensive than the ECM counterparts. But like most technologies, as volumes increase, costs will come down. In fact, some of the latest cell-phone designs have up to four microphones, as OEMs try to get the best recording experience.

Richard Nass is editor in chief of Embedded Systems Design magazine and editorial director of TechInsights' Embedded Group. He can be reached at rnass@techinsights.com.