PORTLAND, Ore -- Micro-electro-mechanical systems (MEMS) microphones have become so much more than smaller versions of the once ubiquitous electrostatic induction based microphones -- electrets -- before them.
MEMS microphones are enabling a whole new tier of "always on" connected, handheld and wearable electronics that will eventually monitor not just our every sound but also those in the environment around us. As such, our devices will not only interpret our voice commands, hand gestures and even the emotions in our voice patterns, but will begin to anticipate our needs by listening to the activity around us and volunteering the information we need at the exact moment we need it.
Once portrayed as a dead-end market destined to become a mere commodity where the most important parameter was cost. Today MEMS microphones have proven that their added value has no bound in sight.
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There are over a dozen suppliers of MEMS microphones worldwide, according to the latest IHS report MEMS and Sensors Report, Microphones 2014 -- with Knowles far ahead of the second-tier suppliers -- many of which are getting their die from Infineon, Omron or MEMSense. Note Akustica is owned by Bosch and Invensense bought Analog Devices MEMS microphone business in 2013. Click here for larger image
MEMS microphone makers worldwide are cashing in on a market that will top $1 billion in sales in 2014 according to IHS Inc. (Englewood, Colo.). The majority of the die inside these MEMS microphones come from just a few suppliers:
Knowles Corp. (Itasca, Ill.) makes its own dies;
Infineon Technologies AG (Neubiberg, Germany) supplies dies to AAC Technologies Holdings Inc. (Shenzhen, China), Goertek Inc. (Shandong, China), Best Sound Electronics, BSE Co. Ltd. (Seoul, Korea), Hosiden Corp. (Osaka, Japan), Gettop Acoustic Co. Ltd. (ShanDong, China) and others;
Invensense Inc. (San Jose, Calif.), who bought Analog Devices unique single-chip CMOS MEMS microphone business in 2013, uses TSMC foundry;
While always using its own interface device STMicroelectronics (Geneva, Switzerland) sources the mechanical chip for some of its MEMS microphones from Omron Corp. (Kyoto, Japan);
A handful of others also make their own proprietary MEMS microphone dies, notably Akustica (manufactured by parent company Robert Bosch GmbH, Stuttgart, Germany), Wolfson Microelectronics pic, Edinburgh U.K. (acquired by Cirrus Logic, Inc., Austin, Texas) is believed by IHS to be using a Teledyne Dalsa Inc. (Waterloo, Canada) foundry;
and several Chinese and Japanese manufacturers are making MEMS microphone die, such as MEMSensing Microsystems Co., Ltd. (Suzhou, China) and New Japan Radio Co. (NJRC, Tokyo).
You still need multiple microphones for directionality -- The wider you space them, the more accurate the beamforming. This is a problem we fight in hearing aids & cochlear implant speech processors due to limited size on the spine of BTE & RIC devices.
Yes, we'll definitely see SNR continue to improve and at lower price points. What is even more important, in my mind, is that a unidirectional MEMS microphone with high SNR can replace multiple-microphone arrays - today. That means, even if the per unit cost is still at a premium, the value prop still makes sense. At a high level, one device means the total system is easier to design and manufacture, less space is taken up on an already tight motherboard, and there will be fewer points of failure (not to mention lower power, heat, etc., etc.). I'm just wondering about uptake of the Harman product though because I haven't seen much written about it to know how well it works.
According to the analysts, all the high-end smartphone makers are going for as much SNR as they can get, and are willing to pay the premium price they demand. The reason is that the voice recognition and noise canceling algorithms work so much better, low-volume voice calls are easier to understand and the quality of the soundtrack on video recordings is even more important than the video quality. Of course, like everything else, as volume production ramps up and prices go down the other-than-top-line-models will start to adapt HD mics too.
In January Harman announced unidirectional analog and digital MEMS microphones with SNR (signal-to-noise ratio) up to 68 dBA. Have you come across anyone designing these in yet? If a single MEMS microphone can replace multi-mic arrays for noise cancelation, it should speed adoption by significantly reducing the cost and space required within the target device. Thoughts?
All your arguements for digital outputs are valid, and in fact the first startup's first microphone (Akustica) had digital outputs. Unfortunately, its kind of like the VHS versus Beta video take war--if you can remember that far back--everybody was already set up for analog mics (electrets) so much so that even Akustica has had to acquiesce a prodeuce analog models. But I am with you, and think hat eventually all MEMS mics will be digital.
It would be interesting to know how far digital microphones (DMICs) -- MEMS mics that include the A/D converter -- have penetrated within the overall MEMS mic market. From an interface perspective, integrating the A/D into the same package as the MEMS makes so much more sense -- especially for applications requiring many microphones (beam-forming arrays, etc.). From the perspective of the audio processor at the receiving end, the two-wire PDM data & clock interface from a DMIC is so much easier to handle than a low-level analog signal, that it's probably well worth the extra cost of the MEMS mics with built-in A/D converters.
Oh that's an answer with fact figures; my estimation was based on the observation of my own. But yes it is very true that MEMS Mics will be having more chances of acceptance in other left out application with possible use of it for betterment.