Bench Talk

Hearables—computing devices that fit into your ears and primarily use an audio interface—received a boost with the launch of Apple’s AirPods wireless earbuds last year. However, AirPods are just a tentative first step for hearables, which are a potentially huge market that still seems up for grabs for whoever can developer a killer product.

Apple’s AirPods are arguably just very well executed wireless earbuds, acting mainly as a peripheral device for mobile phones. But other developers are promising—and occasionally even delivering—much more.

Figure 1: Apple AirPods

Potential applications for hearables span a surprisingly wide range for such small devices. As well as the traditional earbud and headset roles of music and communications, these applications include internet access via the “Internet of Voice,” real-time language translation, and health and fitness monitoring. In addition, developers are trying out “audio curation” ideas, from basic noise cancellation to sophisticated augmented hearing—a kind of augmented reality for your ears.

Dozens of hearable products have been funded. Far fewer have launched successfully. Notable among them are the Bragi Dash, which offers fitness tracking (among other features), and the Doppler Here series, which are noted for their ability to enhance hearing and filter noise. As well as Apple, numerous other major consumer electronics vendors, including Samsung and Sony, are investigating the market.

Hearables have attracted some glowing reviews, with a level of excitement reminiscent of that generated by VR headsets. For example, Wired described the Doppler Here One as  “One of the most jaw-dropping tech demos I’ve tried in a long time. They’re pretty solid evidence that you might want computers in your ears. Soon.”

Demand seems high and a vast global market seems ready. Most of the technological building blocks for a hit hearable are already available, but it’s proving difficult to combine those components together in a compact, reliable package, and to develop software that can unleash the full potential of the hardware. Despite the hype, estimates suggest well under one million smart hearable devices have been sold worldwide.

What’s Holding Back Hearables?

Even Apple’s relatively simple AirPods were delayed for several months. Many less well-funded products have withered on the vine. The ambitious Bragi Dash smart earphones struggled to get to market, and while they have sold well, reviews have been mixed. Doppler’s lauded Here One earbuds also missed their launch date by several months.

“Designing and manufacturing hearables is a lot more difficult that most start-ups imagine,” says Nick Hunn, of WiFore Consulting. “There is a reason why hearing aids are expensive, which is that packing technology into such a limited space is remarkably difficult.”

Developers face several challenges. The greatest is that hearables must be small and light. Therefore, space for batteries, antennas, and user input is limited. Power, in particular, is a problem, with popular hearables only offering about two hours of battery life.

The meager power budget exacerbates other issues, such as wireless communications and signal processing limitations. For example, the obvious wireless choice, Bluetooth, is easily blocked by the water-rich human body. That’s a significant issue for a wireless link between a pocket phone and an earbud, and even worse when sending audio data between two earbuds that have a head between them. Bluetooth also adds unpredictable latency to audio, which gets worse when the signal is weaker. Unfortunately, even 20ms of delay between left and right ears is enough to produce a noticeable echo effect.

Then there are safety and ergonomic issues. There’s zero tolerance for excess heat; batteries cannot ever fail dangerously; materials must be sweat and oil resistant; and a $300 pair of untethered earbuds must fit snugly so they won’t fall out when you stumble, but they can’t be jammed in so tight that they’re uncomfortable.

Finding Solutions

The most successful hearables developers have found passable solutions to some of those problems. A carrying case with a built-in rechargeable battery makes short battery life more tolerable, for example, by making it convenient to recharge earbuds on the go. Latency and signal occlusion problems with Bluetooth prompted developers to explore unfamiliar technologies like Near-Field Magnetic Induction (NFMI) communication. NFMI has a short, two-meter range, but good resistance to absorption by the human body. Doppler’s Here One uses NFMI to send audio between its two earbuds. NFMI also offers resistance to eavesdropping, EMI and multipath interference—a plus for hearable projects.

NFMI is most commonly found in medical hearing aids, which deserve close study by hearables developers because they offer tried and tested solutions for other hearable device challenges—such as durable design, safe materials, and user comfort.

While the body’s absorption of high frequency radio waves remains a problem, recent  refinements of the Bluetooth 5.0 spec, and proprietary extensions like aptX, can at least improve latency.

Still Waiting for the Killer App

Hearables are a fascinating but young market, which seems primed for explosive growth. One analyst forecasts global revenue growing from $15 billion in 2017 to over $40 billion in 2020. These figures include “dumb” hearable products such as headphones, but much of that increase in revenue is expected to come from “smart” devices.

While the many technical challenges and the mixed fortunes of recent hearable projects may seem discouraging, perhaps the real message of all those “near miss” products is that the basic technology is ready, and there’s a huge market wide open for whoever can use existing technology to develop a killer product.