Tiny MEMS Microphone Boosts Audio Quality

Golden Mousetrap 2009 Winner logo

Known as the ADMP421, the new microphone measures a scant 1mm think, thanks to its use of microelectromechanical systems (MEMS)technology. It also offers a flat frequency response to 15 kHz and a bettersignal-to-noise ratio than previous microphones. Analog Devices (ADI), maker ofthe microphone, says it is targeting the product toward the cell phone market,among others.

"Having a smaller and more efficient microphone allowsmanufacturers to build a better phone," notes Todd Borkowski, marketing managerfor ADI.

ADI engineers believe that the new microphone is entering themarket at the right time, especially since standards are changing toaccommodate wideband telephony. "The old telephony standard only went to 3kHz," says Alex Ahenkin, senior acoustics engineer for ADI. "But now that thatthe standard extends to 8 kHz, many of the older microphones won't have thefrequency response to accommodate the higher bandwidth."

Along with the ADMP421's 15-kHz frequency response, ADI saysit also delivers the industry's highest signal-to-noise ratio. The 61-dBsignal-to-noise ratio is reportedly about 6 dB better than predecessors.

"That represents an effective doubling of the distance thatthe microphone can be used at," Ahenkin says.

As a result, the microphone offers an advantage in hands-freephones, which often must pick up sounds at a distance of several feet. It alsocould help in next-generation cell phones that incorporate video. ADI engineerssay that until now phone-based video typically has suffered from lack ofquality audio, but the new system could help because it provides quality audioat a size that's small enough for use in cell phones.

"The emphasis today is on thinness," Borkowski says."In a densely packaged cell phone, every millimeter makes a huge difference tothe cell phone manufacturer."