Has Bone Conduction Audio’s Time Come?

Google has revealed through regulatory filings that Google Glass will incorporate bone conduction audio output in what may be the biggest mass market development for the technology ever, but it will not be the first. Bone conduction audio has existing in some form for almost 100 years, and has a long history of commercialization in both the medical and consumer audio markets, but to date it is a niche technology with adoption concentrated in narrow domains.

Has the time for bone conduction audio for the mass market finally arrived? Probably not yet, but we’re close.

The Origins of Bone Conduction Audio

The general public’s unfamiliarity with bone conduction audio belies its age and the advanced state of the technology’s development. Historically, bone conduction audio has been widely employed as a hearing aid technology – by transmitting sound into the skull audio signals may bypass a defective middle ear, allowing many hearing-impaired or otherwise deaf individuals to hear, even where traditional amplication-style hearing aids are ineffective. A bone conduction hearing aid was first described by Hugo Gernsback in 1923, though the first relevant patent I have located was issued in 1941. Since that time, the technology has improved with lighter weights, new less obtrusive form factors, and higher audio fidelity.

Advantages for All

For individuals with full hearing, bone conduction audio still has several advantages over traditional headphones. For one, it allows the user to keep his/her ears open to environmental noises, which is particularly useful for runners, bikers, and soldiers. Secondly, it allows distinguishable audio to be heard more clearly even over loud environmental noises in environments such as a factory floor. Finally, because there is no need for an air-column between the resonating element and the bone, the device can be waterproofed, which is useful for heavy outdoor use and swimmers in particular.

Commercializing Bone Conduction Audio

Land-oriented solutions have been marketed for years with limited adoption, but there are signs of new interest in the area. At CES 2013, Panasonic unveiled a new design for a bone conduction headset to be released this fall. Distinct from prior headsets offering bone conduction technology, the Panasonic headset will incorporate a bone conduction microphone which will allow buyers to conduct phone calls in noisy environments (for instance, speaking despite wind while riding a bike). Jawbone headsets use the same microphone technology (thus the company’s name) but do not yet offer any bone conduction output.

There has been little development beyond headphones, though in January 2012 Kyocera showed off a “speaker-less phone” (the Smart-Sonic Receiver) which used bone conduction audio that would be silent to the ambient environment, but deliver sound when pressed against a user’s head (as if receiving a call with any other phone). The technology was later packaged for consumers as the Kyocera Urbano Progresso (more details). It appears the phone is only available in Asia.

Despite these commercial products, less expensive ear buds are still king of the hill for personal audio. Ear buds are likely to maintain dominance in the music-headphone space because of certain drawbacks related to conduction audio. For one, it is more difficult to pinpoint sounds in space with conduction audio because the signals travel to both ears – therefore it is more difficult to achieve binaural stereo or surround-sound effects. Secondly, the skull conducts lower frequencies better than air (as Wikipedia notes), which is one reason your voice sounds different in your head than in a recording. This will alter the equalization of music, which might be synthetically rebalanced (I suspect) but won’t ever appeal to audiophiles.

Rather than music, bone conduction audio is best suited to digitalized conversation and other types of audio in which balance and frequency range are less important. An era of hands-free communication and ubiquitous computer I/O is perfectly suited to that use case.

Moving Forward

It remains to be seen whether Google Glass changes our daily lives as much as Sergey Brin hopes, but it is an ideal use case for bone conduction audio given the potential to develop apps that focus on use-cases beyond music: phone calls, e-mail text-to-speech, spoken navigation, alerts, etc. Furthermore, Google Glass is designed to be daily-wear, meaning it would theoretically be worn during a business meeting, at lunch, in traffic, while visiting Grandma, etc. This was never possible or socially appropriate with a Bluetooth headset which disrupted environmental hearing in one ear. (The other problem being it rudely conveys that you may take a call at any second regardless of your current social context, a problem that Google Glass may not overcome). Whether bone conduction audio can ride Google Glass’s coattails to glory depends on whether Google Glass truly succeeds as a ubiquitous wearable computing device. Only if adoption is strong will the market take notice.

Even if it does succeed, however, it is not the final evolution of bone conduction audio. Although Google Glass packages the entire device, including audio, into a fairly small form factor, existing technologies allow bone conduction receivers to practically vanish. The paragon of bone conduction hearing aids today utilize skull-implanted receivers, or at least anchors, to transmit sound with greater clarity and without weighing on the ear’s pinna or requiring a headband as traditional bone conduction hearing aids do. Such bone-anchored hearing aids can either involve a titanium screw that protrudes through the skin that is used as a mount and vibration-conductor for an external and removable signal processor, or a magnetic implant sealed beneath the skin that performs a similar function. While the external paired-devices are fairly large (slightly smaller than a matchbook), if the processing power was offloaded to a phone or eye wear they could be almost invisible, if not completely someday.

I imagine a day not too far off when first body-hackers and then the general public are incorporating invisible input and output into their bodies with minimally invasive surgery. While I will address the considerable ethical and privacy concerns this raises, it is an intriguing thought from a technology standpoint. If we are truly seeking to liberate ourselves from carrying around devices (which Brin has called emasculating), then this is a logical progression. That said, it may come to pass that we short-circuit that technological evolution by skipping directly to neural implants which could provide visual and other sensory input as well. More to follow on that though.

Regardless of whether bone conduction audio takes off as a result of its incorporation into Google Glass, I am excited to watch the technology develop as innovators look for new and more streamlined ways to help humans interface with the devices around and on us.

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