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How Excellent MEMS Microphones Turn Laptops into Communication Systems

IMAGE: SHUTTERSTOCK

The first smartphones used electret con- LAPTOPS AS CONFERENCE SYSTEMS conversation. A high AOP gives an undistorted
denser microphones with about 60 dB SNR Like smartphones, conference systems or input, even in the loudest surroundings. With
and an approximately 10 mm diameter. Later, smart speakers also use MEMS microphones tight mic-to-mic matching, the performance
smaller MEMS microphones became more to pick up voice signals. However, the of beamforming algorithms is improved.
prevalent. Finally, in 2018, Infineon launched requirements for these applications are even But just in the last year, the pandemic
the XENSIV™ IM69D130 MEMS microphone higher. These microphones must deliver low has led to more and more standard laptops
with 69 dB SNR, setting a new performance self-noise for natural sound — similar to that being used as conferencing systems. However,
benchmark in audio. a user would experience in a face-to-face today’s built-in microphones fall short of the
expected sound quality and experience. Users
don’t want to wear headsets all day. Nor do
they want to constantly lean over their device
to be understood. Instead, they may even
want to get up during a conversation to move
around and still be heard.
Of course, the sound is determined by
several factors. For example, as mentioned
above, various software algorithms are
used that could have an influence on audio
quality. Infineon engineers therefore wanted
to find out how big a role the microphone
actually plays.
For this purpose, the test setup shown in
Figures 2 and 3 was utilized. A loudspeaker
(“artificial mouth”) plays back real speech,
which is picked up by the microphone in the
device under test (DUT) laptop. The DUT
processes the recording and transmits it to
a reference computer. The received data is
compared with the source data.
To objectively evaluate the quality and
intelligibility of the recordings, the analysis
was performed according to the Perceptual
Objective Listening Quality Analysis (POLQA)
standard. The resulting mean opinion score
(MOS) was compared for the laptop’s built-in
standard microphone (<65 dB SNR) and
Figure 4: Results of the microphone test. The microphones with high SNR achieve a Infineon’s XENSIV™ IM69D120 (69 dB SNR).
significantly higher MOS score. Both microphones have the same sensitivity

JUNE 2021 | www.eetimes.eu