MEMS microphone technology adapting to changing use cases: Page 3 of 5

April 13, 2017 // By Masahito Kanaya
Owners of devices such as smartphones and tablets continually want to be able to use their gadgets in new ways, and at the same time expect extremely high performance. On-board audio functionality is a prime example. People want to be able to record social events, music performance and expect accurate, lifelike playback, or to enjoy high voice-call quality free of background noise even when outside or travelling in a car. There is also demand for high audio quality when capturing sounds further from the microphone.

With the advantages of high noise immunity and simplified circuit design, digital MEMS microphones lend themselves well to use in multi-microphone arrays for echo and noise cancellation, as well as beamforming to achieve directional sensitivity.

To implement noise cancellation in a smartphone, a common approach is to position one or more extra microphones away from the main voice microphone, such as in the upper edge or the back of the case, to detect noise from the surrounding environment. This can be subtracted from the output of the voice microphone to help improve call quality. The noise-reduction microphones are often also used in video-recording modes.

Beamforming, also, uses an array of two or more microphones. Although most microphones have omnidirectional sensitivity, some applications can benefit from increased sensitivity in a particular direction or reduced sensitivity in others; for example to improve audio quality and intelligibility in situations such as audioconferencing or in-car calling.

Beamforming makes this possible by applying digital algorithms to the outputs of microphones in the array, based on the phase differences of sounds arriving from various directions. It is also possible to identify the direction a particular sound is coming from.


ASIC design in detail

Microphone module makers differentiate their products by choosing a suitable MEMS microphone kit, in which an optimized pair of MEMS sensor and ASIC is already combined.

Figure 3: Microphone specialists choose a suitable MEMS microphone kit.

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