High signal-to-noise ratio microphones are turning laptops into all-round communication hubs

A large number of employees continue to work from home or in hybrid mode. Although some organizations have largely returned to "normal", many people have become accustomed to online meetings. Without face-to-face meetings in the office, efficient communication relies on good tools, such as video conferencing software, computer hardware, etc.

Twenty years ago, few laptops had built-in microphones. But now, nearly every laptop on the market comes with a webcam and one or more microphones—essential collaboration tools for colleagues when they’re not all in the same room.

In this article, we explore the laptop's transformation from a word processing tool to a studio-grade communications device and the technology behind it.

Microphones and webcams are becoming ubiquitous

The integration of microphones into laptops marked the transformation of these machines from simple word processors and number-crunching devices into communications platforms.

As more and more people abandon desktop computers and choose laptops, it is clear that consumers do not want to be dependent on peripherals. In order to cater to the market, manufacturers began to integrate peripherals into laptops to reduce the need to use peripherals to perform specific tasks. Instead of external USB hubs, laptops have built-in USB ports; instead of WiFi dongles, wireless network cards are integrated; instead of mice, multi-touch trackpads are used.

As high-speed Internet and video calls became more popular, manufacturers began to integrate webcams and microphones into the screen bezels of laptops to meet the needs of online communication. For example, Apple first launched the first generation 15-inch MacBook Pro1 with a built-in iSight camera and microphone in January 2006.

By the late 2000s, most performance-oriented laptop models came with similar hardware, and by the late 2010s, nearly all laptops (including the most affordable models) came with a webcam and microphone.

High signal-to-noise ratio microphone turns laptop into a complete communications device

The next wave of upgrades in laptop peripherals is coming: high signal-to-noise ratio microphones using MEMS technology. This technological advancement heralds a change in the way we think about using laptops.

As the coronavirus pandemic and other factors have shifted us from working in offices to working from home, the next generation of microphones will allow us to stand up and move around; allowing multiple people to speak into the same microphone while still having high-quality sound.

SNR

SNR is not a technology, but a metric for evaluating microphone quality. It stands for signal-to-noise ratio. In a voice call scenario, SNR measures the ratio between the voice of a colleague (or other caller) on the call and the noise transmitted by the microphone. Noise comes from multiple sources, including environmental noise, electromagnetic interference, and mechanical vibrations of the microphone.

MEMS microphones

One of the core advantages of MEMS microphones is that they can be manufactured in large quantities using silicon wafers. This means that the manufacturing process is similar (but not identical) to microchip manufacturing. This approach ensures small device variations, meaning the production process is very reliable.

Unlike traditional condenser microphones, MEMS microphones mainly use capacitive sensing technology to convert air movement into digital signals. MEMS sensing elements are combined with low-noise ASICs. Due to the use of microprocessing technology, MEMS microphones can be very small, therefore, suitable for packages below 10 mm2.

Case Study: Turning a Laptop into a Communications Device

In a recent experiment, technology company Infineon Technologies demonstrated the benefits of high signal-to-noise ratio XENSIV™ MEMS microphones in communications. As shown in Figure 1, the team designed a scenario using an artificial mouth and a laptop facing the artificial mouth to receive sound signals, with a variable distance between the two. The experiment was completed in a system partner laboratory of Infineon Technologies in China.

The experiment assumes that MEMS microphones can provide good results at larger distances between 3-5 meters. Then, 4 different scenarios were tested: a laptop with a traditional microphone and a laptop with a high SNR MEMS microphone, as well as speech signal processing with and without VoIP service in both scenarios.

Comparing the playback speech captured by the microphones with the original files, the results showed that the high SNR MEMS microphone performed better than the traditional laptop microphone in both cases. The real test was to see if people also perceived the sound quality better. To do this, they compared the mean opinion scores (MOS) of the two microphones. As shown in Figure 2, the Infineon microphone achieved a 20% improvement in sound quality at close ranges of 1-3 meters and a 35% improvement in sound quality in conference scenarios of 3-5 meters!

Figure 1: Test setup at Infineon’s partner lab [6]

Through this test, we can see that in the future, using laptops as communication devices will achieve a more natural, studio-grade experience.

Figure 2: XENSIV™ MEMS microphones have a higher MOS score

(Image source: Infineon)

The Future of MEMS Microphones

MEMS microphones, with their small, digital, and high-quality features, allow us to seamlessly switch between different conversations and devices, even without sitting at a desk with a traditional fixed microphone. Imagine being able to walk from one room to another while you are on the phone with someone. Equipped with a high-SNR MEMS microphone in each device, it will ensure better sound pickup, which allows the algorithm to work better despite the ambient noise and the changing distance between you and the receiver.

With the ability to provide studio-quality sound pickup, MEMS microphones can even achieve podcast-like audio quality without the need for equipment such as external microphones.

The way we communicate for work and entertainment is changing - there are more and more voice-based communication methods, such as: phone calls, voice messages, podcasts, and social apps like Clubhouse.

There are many applications for microphones in IoT devices beyond laptops. Voice-controlled assistants are already common, and voice user interfaces are expected to be used in many other smart home devices. They are not only technological innovations, but also represent a shift in the way we work and live.

Shop Infineon Microphones

Infineon is one of the few microphone manufacturers that can deliver on the promise of high SNR MEMS microphones. They produce both bare MEMS and ASIC die as well as packaged microphones that combine the two. Their XENSIV™ series of MEMS microphones are designed for laptops and other devices to improve call quality3.

Figure 3: Photo of the XENSIV™ MEMS microphone (Source: Infineon Technologies)

The XENSIV™ family has several models available now, with several new models coming soon.

When choosing a XENSIV microphone, you must first determine what interface your application requires. Infineon offers digital microphones with PDM (Pulse Density Modulation) interfaces and analog microphones with differential and single-ended interfaces, covering all the most common interfaces on the market.

The choice of interface depends mainly on the front end of the system SoC. The digital PDM model consumes 980 µA – although a low-power 520 µA model (IM69D128S) is already in production. The analog differential interface model consumes even less at 170 µA. The IM68A130 consumes only 110 µA.

These requirements alone will narrow the Infineon XENSIV catalog to a few options. From here, it’s time to choose the product with the right balance of sensitivity, SNR, and acoustic overload point (AOP) for your application.

Most models in the XENSIV catalog use Sealed Dual Membrane (SDM) MEMS technology and are rated IP57, providing premium protection against water and dust, helping you design this microphone into your next product.

References

1. Apple. 15-inch MacBook Pro Developer Note. Developer Connection [Internet]. 2008 Oct 10. Available from: https://web.archive.org/web/20081010192847/http://developer.apple.com/documentation/HardwareDrivers/Conceptual/MacBookPro_0601/Articles/MacBookPro_0601.html

2. Mike Levine. The shape of things to come: Different types of microphones and when to use them. Popular Science [Internet]. 2022 Mar 6. Available from: https://www.popsci.com/reviews/types-of-microphones/

3. Infineon. MEMS microphones for consumer. Infineon [Internet]. Available from: https://www.infineon.com/cms/en/product/sensor/mems-microphones/mems-microphones-for-consumer/

4. mynewmicrophone.com. What Is A Good Signal-To-Noise Ratio For A Microphone? [Internet]. Available from: https://mynewmicrophone.com/what-is-a-good-signal-to-noise-ratio-for-a-microphone/

5. mynewmicrophone.com. What Is A MEMS Microphone? (Micro-Electro-Mechanical Systems). [Internet]. Available from: https://mynewmicrophone.com/what-is-a-mems-micro-electro-mechanical-systems-microphone/

6. EE times.com. How Excellent MEMS Microphones Turn Laptops into Communication Systems. [Internet]. Available from: https://www.eetimes.com/how-excellent-mems-microphones-turn-laptops-into-communication-systems/