Headsets that steady the mind: Advanced laboratory offers many acoustic environments

29 speakers are placed in a hemispherical shape all around the test object in the middle. This means that EPOS can simulate a myriad of acoustic environments in one of its two laboratories. Illustration: Epos

Clap. The sound of two hands clapping against each other dies out, almost even before the hands part again.

We are in an almost anechoic room that belongs to EPOS, Danish manufacturer of audio equipment in Ballerup, and with a single press of a button, a panel opens on each wall. After 30 seconds of humming from a range of small electric motors, the sound is completely different.

The clap resounds for a second, and when we speak, the reverberation floats around the small laboratory because the sound is now reflected instead of being absorbed by the acoustic panels.

A flexible system of movable acoustic panels and curtains means that EPOS can change the reverberation of the room by up to a second in just a few moments.

“We have measured a reverberation of just 32 milliseconds. When we test equipment for the major video conferencing providers such as Zoom, Microsoft Teams, and Google Meet, the requirement for testing is usually 100 milliseconds, so we are well below that,” says Jesper Kock, Vice President, Research & Development.

The small anonymous lab does not look like much at first glance, but it is designed down to the smallest detail in order for EPOS to be able to control the reverberation very accurately when testing their headsets, which are primarily developed for gamers and for enterprise customers in office environments.

The article continues below the picture.

Jesper Kock is Vice President of Research & Development at EPOS—a relatively new audio brand formerly known as Sennheiser Communications. Illustration: Epos

The angled wall

For example, the four walls are not parallel to each other. One of the walls is placed at a three degree angle to avoid flutter echo that can occur when sound waves are transmitted between parallel walls. Even a regular office can have so many variables that it is almost impossible to simulate every conceivable situation because there are so many degrees of freedom in a three-dimensional room. If the frequency is doubled, the problem becomes eight times as big because there are three dimensions.

When moving outdoors, the amount of variables explodes, and that’s exactly what many headset users have started to do. While we mostly just sat at home in front of the screen in the first months of the coronavirus pandemic, the situation is now more hybrid. Some are at home, others in the office, and still others in the car or train during the morning status meeting.

“The amount of different acoustic environments you move through is huge: from the time you get up from the office, walk out the door, get on a train, get off, get on your bike and pick up your kids, and finally walk through the door at home. With a conversation over the headset the whole way. We must take this chain into account with one headset, where we previously had solutions for each environment. Similarly, gamers take their headset to school and listen to music on the road,” Jesper Kock says.

Another laboratory is therefore equipped with 29 speakers placed at three different heights in a half dome with a chair in the middle. From there, EPOS can simulate a myriad of different acoustic environments because the speakers can play sound from all sides.

The article continues below the picture.

Illustration: Epos

One almost instinctively ducks their head a bit as the roaring engine sound of a plane taking off is completely turned up. The sound rolls from the floor on the left side up over the head and disappears up into the horizon to the right in the second sound laboratory.

New ways, new challenges

Speech comprehension, reverberation, and signal/noise conditions are some of the most central parameters that EPOS measures in the new laboratories.

“We supply products for many different systems, e.g. Zoom, Teams, or Google. In the past, it took us quite a few hours to set up a laboratory for a specific setup. Now we can change the reverberation and the acoustic environment in minutes. That way, we can train our algorithms and stress our products more efficiently,” Jesper Kock says.

When we start communicating in new ways, new technical challenges usually also arise. An increasingly familiar problem with video conferencing is when a person wants to interrupt the speech flow of a colleague. It’s called overlapping speech. The challenge arises because most meeting systems today are so sensitive and effective at removing the echo that occurs when a person speaks into a microphone, which is then reproduced in the video meeting and picked up by the microphone again.

Many video systems have difficulty distinguishing between an echo and a new voice breaking into the voice stream, so the first part of an interruption is completely cut off, which is not acceptable.

“A combination of a robust acoustic system, digital signal processing, and large enough amounts of data is required before the system itself learns to distinguish between a real interruption and just a residual of something that has already been said,” Jesper Kock says.

From the ear to the brain

Although EPOS is a relatively new audio brand, the company stands on the shoulders of a long Danish tradition of hearing aids. Jesper Kock himself is a good example of this. He started his career developing hearing aids at Oticon and later switched to Sennheiser Communications, which is today EPOS.

EPOS and Oticon are both part of the Demant Group and therefore share the longer-term development work at the Eriksholm Research Centre in Helsingør. And although both hearing aids and headsets are placed around the ears, most research and development does not focus on the ear at all.

“The ears are really just a channel that distributes signals to the brain, which processes and analyses the sound. It is the brain that decides which frequencies to turn up and down. That is why much of our research is currently focused on the brain,” Jesper Kock says.

Active noise reduction is therefore not only about improving speech comprehension, but also ensuring the brain can work in peace. We know this from long flights, where one often gets extra tired—despite taking a good nap during the trip. This is because the brain is constantly working at high pressure to remove the background noise from the aircraft’s powerful jet engines. The more unnecessary noise a headset can filter out so that the sound does not reach the brain, the less energy needs to be used.

Waves in coronaland

The coronavirus pandemic has at the same time led to technological leaps in development as well as a supply nightmare for EPOS.

“In just a few months, we gained 10 years of training in using video conferencing and hybrid work with headsets. Even 10-year-old school children today use Teams and Zoom without instructions. When we launched EPOS in 2019, we actually spent a lot of energy convincing large organizations of the benefits of online meetings and hybrid work,” Jesper Kock says.

A major explanation for the fact that EPOS and the rest of the audio industry today can supply small wireless headsets with built-in noise reduction is the general development in microchips, where Moore’s law has since the 1960s provided more computing power with more transistors that take up less space and have a lower energy consumption.

But when the coronavirus pandemic came rumbling from Wuhan in China, it also became the starting point of a global shortage of just that type of microchips. The car industry has had to introduce closing days at many factories, and today there are still long waits for various types of consumer electronics, such as graphics cards for gaming. At EPOS, they have partially avoided the chip shortage by investing heavily in the beginning.

“Early on, we tied up a lot of capital in the purchase of chipsets, and that assessment proved to be correct. But we have also been forced to redesign certain products in order to keep them in production,” Jesper Kock says.

Revival of DECT

It is small details that reveal that EPOS focuses on gaming and enterprise as its primary users. While most wireless audio solutions today use Bluetooth, EPOS’s enterprise headsets also have the ability to connect with the otherwise somewhat dwindling DECT protocol, originally developed for cordless landline phones.

“It has a long range and can handle many users in a small space. The increasing use of Bluetooth, which has actually been developed for data transfer, means that we are experiencing instability, Jesper Kock says.