How MEMS microphones link the real and the digital world – part 1
When we think of microphones, we typically imagine a cylindrical rod with a spherical top that a person is singing into. But nowadays, microphones are not only found on stage, in recording studios, or on film sets but all around us – from smartphones and earbuds to smart TVs and doorbells. They are important building blocks to link the real and the digital world – the ears of our devices.
In this first of two-series blog post, we will take a look at the technology behind MEMS microphones and why their advantages have led to a rapid uptake in the market. In the second post, we will take a deeper look at MEMS microphone applications, markets, and their role in Smart Cities in project MARVEL.
Introducing: MEMS microphones!
In essence, a microphone converts sound waves – air pressure – into an electrical signal. But what sounds simple in theory is complex to implement in practice. The aforementioned professional microphones are expensive, large and often limited to a certain use-case, whereas audio capturing for consumer devices requires robust, small, and mass-producible sensors. This is where semiconductor technology comes in.
MEMS (Micro-Electro-Mechanical Systems) microphones are small mechanical structures that convert sound waves into electrical signals. These microphones consist of a MEMS, an ASIC and a package.
The MEMS is the actual sensing element: A membrane and a backplate form an electrical capacitor. When a soundwave moves the membrane, the resulting change in capacitance is extracted as an electrical signal. The Application Specific Integrated Circuit (ASIC) amplifies the small electrical current created by the MEMS and sends the analog or digital signal to the device the microphone is connected to through the package, which encapsulates and protects the sensing elements.
MEMS microphones are now the standard audio sensors outside of professional audio recording settings. Their characteristics make clear why that is:
- Size:
- MEMS microphones are typically not larger than 4 x 3 x 1.2 mm – and can be even significantly smaller.
- Mass producible:
- As they are manufactured using semiconductor processes, MEMS microphones can be produced on a large scale, with the tight matching between devices and few process variations.
- Acoustic performance:
- With the latest technology advances, MEMS microphones can pick up sounds across the whole application spectrum – from quiet whispers to the loudest signals. Among the most important performance parameters for a microphone are the signal-to-noise ratio (SNR), the acoustic overload point (AOP), and the power consumption. Maximizing SNR and AOP while minimizing power consumption continue to be among the most important areas of innovation in the MEMS space, allowing for even better performance.
Blog signed by: IFAG team
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This project has received funding from the European Union’s Horizon 2020 Research and Innovation program under grant agreement No 957337. The website reflects only the view of the author(s) and the Commission is not responsible for any use that may be made of the information it contains.
