Knowles is a market leader and global supplier of advanced micro-acoustic, audio processing, and specialty component solutions, serving the mobile consumer electronics, communications, medical, military, aerospace, and industrial markets. Knowles uses its leading position in microelectromechanical systems (MEMS) microphones and strong capabilities in audio processing technologies to optimize audio systems and improve the user experience in smartphones, tablets, and wearables. Knowles is also a leader in acoustics components used in hearing aids and has a strong position in high-end oscillators (timing devices) and capacitors. Founded in 1946, Knowles has employees in 15 countries around the world.
One of the first things you notice about a new smartphone is that it is remarkably thin. Most typical handheld models hover around the seven millimeter range and weigh in at about 150 grams. Sleek certainly, but how do engineers design all those components – camera, microphone, loudspeakers, battery, touchscreen, processors, network and power controls, antennae and memory ‒ into such a super-skinny package?
At the beginning every single component needs to be as small as possible, as light as possible and as inexpensive as possible while still doing its primary job. Fortunately, there are people like Andy Unruh, an acoustics engineer and algorithm developer who works for Knowles, a world-leading company in designing audio solutions for mobile consumer electronics.
Unruh has a unique job designing the components, systems and algorithms for miniature audio and micromechanical technology. His job is to make certain that Knowles’ pioneering technology, like the groundbreaking SiSonic™ microelectromechanical systems (MEMS) microphone and the powerful micro speaker, Cobra™, are placed optimally for the best possible performance according to the customer’s product design and specifications. In the past, this meant testing the sound quality and algorithm functionality on the actual physical hardware and prototypes of a pretty diverse product range including smartphones, smart watches, headphones and hearing aids. Today, the process has changed.
Making a smartphone sound good is not as easy as it seems. There is so much more to think about than just capturing and transmitting audio signals. Today, everything is so small, and there are many more quality factors to consider – not to mention exacting customer specifications. Sound quality factors can include everything from echo cancellation and noise suppression to correcting the sound quality according to the type of room or location.
To manage this differentiation, Unruh started to rethink his lab’s testing processes and considered how changing the process could help create even better acoustic products for Knowles customers. He knew that he would need to integrate simulation software into the process on a more formal basis, and Simcenter™ 3D for acoustics simulation software, of the Simcenter™ portfolio from Siemens Digital Industries Software, was high on the list.
“My idea was to replace some of the actual physical measurements with simulation,” explains Unruh, a senior principal engineer. “It is very time-consuming to do these physical measurements. Many times, the tests need to be done at the customer site and the customers don’t really enjoy us tying up their anechoic chamber for weeks at a time. Often times, we get the measurements back and we realize that they are flawed and we have to go and do them all over again.”
“We started with the idea of homemade software. When I crossed-checked it against physically gathered test data, the correlation wasn’t strong enough. So we moved to the idea of a finite element package to replace the physical measurements. But there weren’t that many solutions to choose from. I talked to a few people and Simcenter 3D for acoustics simulation was one of the options.”
With many configurations and a wide hertz testing range, usually from 20 to 8,000 Hz, acoustic simulation is data heavy and requires considerable computing power to do the number crunching. This is why specialized companies like Knowles are only now turning to virtual simulation. Previously the cost of computing was just not worth the investment.
“We have tested with a few example problems to see how well the Simcenter 3D for acoustics simulation package supports us and it passed with flying colors,” notes Unruh. “Today, we use Simcenter 3D for acoustics simulation on our customers’ products and as a research tool to replace in-house physical measurements.”
Simcenter 3D for acoustics simulation helps Unruh’s team identify the optimal locations for primary and secondary microphones in devices like tablets or mobile phones. The software considers the physical phenomena of the human head, including tilt and facial distance from the microphone, as well as the overall generic environment, like a conference room, small office or outdoor area.
Microphone and speaker placement aren’t the only factors to consider. Algorithms play a very important role in the design and development process, smoothing out sound quality issues in a variety of these situations. One of the main tasks that Unruh and his team do is to develop and test new acoustic algorithms according to the customer specifications. In the past, this was entirely a physical testing environment with various standard test set-ups and microphone positions to run the product through a handful of standard test scenarios.
“As you can imagine, our testing wasn’t comprehensive,” Unruh says. “Now, with Simcenter 3D for acoustics simulation, we are able to do much more extensive testing virtually. We can do thousands of microphone combinations in all types of different rooms and usage scenarios. We can take into account different reverb times. We get much better coverage when we test our new algorithms using Simcenter 3D this way.”
From the customer perspective, adding simulation into the mix has resulted in a better product. By testing more and different scenarios virtually, the team can easily spot potential problems. There is much less chance that an algorithm has a flaw in it. The team can easily identify whether one doesn’t work well with a certain type of reverb in a room, or doesn’t work well in small rooms, for example.
“We can test for all types of cases and scenarios virtually, whereas before we had a test room and we would have tested a couple of scenarios per product,” Unruh says. “Simcenter 3D for acoustics simulation gives us extra flexibility as well. In the past, if a customer decided to change the microphone placement, there would be a really good chance that we would have to redo the algorithm.”
“Today, we have a huge variety of options that we can examine and suggest to the customer,” adds Unruh. “We have really good coverage with our virtual testing based on Simcenter 3D for acoustics simulation and can be confident of what we do.”
Unruh also likes the flexibility of Simcenter 3D for acoustics simulation. Mobile phones require acoustic echo cancellation and it was easy to include this specific task in the Simcenter 3D solution. “It easily simulated the linear echo path,” Unruh explains. “We are using Simcenter 3D for acoustics simulation very successfully to train our algorithms. When we checked the simulated coherence versus an actual tested coherence, the results were right on top of each other on the grid. It was amazing.”
Any acoustic specialist will tell you that there are certain things you cannot model virtually. The Knowles team still needed a starting point, one physical measurement that anchors all the other measurements.
“We formerly had to do about 100 physical measurements and now this is down to one,” says Unruh. “Once we have that one physical measurement, we can use it to scale the rest. Everything comes into line. The significantly reduced testing time has a huge impact on our budget. We estimate our cost saving could be $7 million per year depending on our annual number of customers.”
With the basics under their belt, the Knowles team members are planning to take advantage of more of the automated tools available in the software. They have a goal of 24-hour turnaround. This means that from the time the customer provides the phone dimensions and specifications for microphone placement, Unruh and his team can come back within a day’s time with the optimal placement and performance quality. “Currently this takes months,” says Unruh. “It is a little faster now. Obviously, like every industry, we want to get into the design process early and advise our customers where the optimal microphone position will be for their product. The only way to do this is via simulation solutions like Simcenter 3D for acoustics simulation.”