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Assessing the feasibility of Bluetooth in hearing rehabilitation

Yanz, Jerry L.; Preves, David A.

doi: 10.1097/01.HJ.0000299173.90281.c0

The authors foresee a combined hearing aid-Bluetooth receiver that can put users “in touch with the world in a way that nothing else can.”

Jerry L. Yanz, PhD, is Senior Staff Audiologist and David A. Preves, PhD, is Senior Staff Engineer, both at Starkey Laboratories. Readers may contact Dr. Yanz at

Bluetooth is taking a bite out of the wireless marketplace. In the midst of a variety of other wireless alternatives, the growth of Bluetooth products since the introduction of the protocol in 1994 has been phenomenal. Beyond its initial use in cell phones, Bluetooth technology is an accessory in many automobiles, MP3 players, wireless watches, jewelry, and toys, just to name a few.1 In fact, Bluetooth technology has been incorporated in the NOAHlink programming device (HIMSA) to eliminate the bothersome wires that traditionally have connected the host computer to the hearing aids that are being programmed.

With its inherent features of security, portability, robustness, low power, and low cost, Bluetooth is also an obvious candidate for applications in hearing instruments. As this paper will make clear, however, practical limitations with the current Bluetooth standard are limiting its application to hearing aids, and Bluetooth technology will not become accessible to the majority of hearing aid wearers until these limitations are resolved.

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Bluetooth is a digital wireless protocol designed to achieve wireless connectivity among computers, digital mobile phones, and various other devices. A Bluetooth signal differs in one basic aspect from the FM (frequency modulation) transmission that has been utilized for years in many hearing assistive devices: Bluetooth employs digital FM, whereas the older technology has used analog FM.

There are several ways to get a signal from a Bluetooth receiver into a hearing aid, as shown in Figure 1. The only commonality across these options is a Bluetooth digital signal at the beginning and a hearing aid at the end of the line.

Figure 1

Figure 1

Bluetooth integrated circuits have required too much battery current and occupied too much space to be incorporated directly into hearing aids. Instead, Bluetooth signals have been made available to hearing aid wearers via external accessories, packaging the Bluetooth chips in add-on modules or remote devices.2 Almost all these devices are relays in which information is transmitted via Bluetooth from an external device to an intermediary device and then relayed to the hearing aid via direct electrical connection, induction, FM, or a proprietary wireless transmission.

Some of these devices use the Bluetooth relay in a bi-directional mode, also relaying information to the outside world by the same means listed above through an intermediate device and then to an external device using Bluetooth. The most obvious use for bi-directionality is to support telephone communication. Still, the most useful implementation of Bluetooth technology for hearing aid wearers, embedded directly in the hearing aid itself with no additional peripherals, does not exist.

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Use of Bluetooth being encouraged

As an example of support for these developments, the BlueEar Assistive Listening System consortium was formed in 2000 with encouragement from the European Commission to develop product lines that establish connectivity with hearing aids using Bluetooth technology.3 The project objectives were to: specify the needs of an assistive listening system, develop an open standard, develop a prototype application and a range of prototype products, and validate the system functionality of the prototype application with users.

Cited in the BlueEar documents are the benefits Bluetooth could bring hearing-impaired persons when compared to: (1) induction loop systems, which have hum and limited audio frequency range, and (2) FM systems, which do not have a secure wireless link and support only one-way communication. BlueEar's vision is that by 2010 hearing aid wearers will be able to switch their hearing aids to a common channel and pick up sound anywhere in Europe.

The main contact for this project was Gn Transistor Ab, and other members included the Institute for Rehabilitation Research (The Netherlands) and three associations of persons with a hearing disability: Hoerselskadades Riksfoerbund (Sweden), Hearing Concern (United Kingdom), and NVVS (The Netherlands).

Prototypes were presented at a workshop in the UK in 2003. Thirty attendees specified their listening system requirements and evaluated the mockups of proposed BlueEar systems. Since users expressed the need for a wireless interface built into the hearing aid, a liaison was established to raise awareness of this need within the hearing aid industry. The project was closed on September 30, 2004, after seemingly achieving somewhat inconclusive results.

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Slow acceptance of Bluetooth hearing aid accessories

Despite their great promise, at the time of this writing Bluetooth accessories for hearing aid wearers have not seen high-volume use in the market. Let us consider why such Bluetooth devices have not reached the mainstream of the hearing healthcare distribution system and examine the feasibility of incorporating Bluetooth inside hearing aids (e.g., Hagedoorn4) rather than as an accessory.

The Bluetooth products for hearing assistance marketed so far via conventional audiology and hearing aid specialist channels can be viewed as representative examples of a new technology going through early stages of its life cycle. An examination of the nature of technology adoption in the market may shed light on how we arrived at the present status and the future possibilities for Bluetooth in hearing healthcare.

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Moore describes the phases of a technology adoption life cycle, which has been called the foundation of a high-tech marketing model.5 He defines this model as a Gaussian distribution for classifying consumers according to their response to discontinuous or disruptive technologies, namely those that require consumers to change their current mode of behavior in using products and services.

The customer classifications in this model—Innovators, Early Adopters, Early Majority, Late Majority, and Laggards—can be characterized by the degree of enthusiasm they have for innovative products and by how forgiving they are of initial idiosyncrasies, imperfections, and the learning process that often accompanies new product developments (see sidebar). A successful new product progresses through all of these customer types in the marketplace.

Along this product life cycle, a chasm or gap exists between the Early Adopters and the Early Majority. When a new product reaches this phase, it may not yet have generated sufficient revenue to support the investment in its ongoing development. And if developers fail to resolve issues that have arisen in its initial release, the product may never be accepted by the Early Majority. Many new products never make it past this chasm to gain widespread acceptance in the market.

The pace of new technology development and performance improvement often outstrips what markets need (or what consumers can absorb). Phases of product cycles are sometimes driven by product performance that overshoots market demands. Products arising from disruptive technology may initially have performance issues in the form of bugs and reliability problems that have not been completely shaken out, and they will likely have lower profit margins than established products. These are attributes that the most profitable customers of successful companies don't want to bother with.6

After reflecting on this model, we can speculate that the cutting-edge Bluetooth products cited above represent early innovations rather than mature products. Many of these products were extremely exciting when first introduced and purchased by Early Adopters, but have not progressed to the next stage to be accepted by the Early Majority buyers.

Why is this the case? Many of these current Bluetooth products for the hearing health field are inconvenient to use because pairing the two devices is difficult, and the wireless connection can be lost during use and be difficult to re-establish. Additionally, some of these early Bluetooth products have battery-charging issues.

These reliability and convenience-of-use issues seem to fit with the Early Adopter category and chasm outlined in the technology adoption model and may help explain why at least some of the currently available Bluetooth assistive listening device products have not been accepted into the mainstream hearing rehabilitation market.

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Bluetooth can deliver a low-noise, secure, wireless signal over a well-defined transmission range. Two obvious Bluetooth applications for hard-of-hearing people are to facilitate telephone communication and improve speech intelligibility in noise. At a lower priority (but only slightly in some people's eyes) are entertainment applications, such as listening to television and music.

Realizing the benefits of Bluetooth technology requires that developers and manufacturers engage the full progression of customers described above. To date, all Bluetooth hearing aid applications require extra equipment. This alone is a deal breaker for many potential customers, since most hearing aid wearers prefer to conceal their gadgetry. Therefore, the target group most likely consists of people who are already using hearing aids well and who also realize the potential for even greater benefit if they adopt the additional technology. We might expect the first users of Bluetooth to be people with moderate or greater hearing loss, who already wear BTE devices and see the value of adding the accessory.

Alternatively, as described earlier, a disruptive technology is typically most successful if presented to a new market, rather than the existing market. If this is true, then perhaps it should target people with borderline losses, who are not yet hearing aid users and are open to new alternatives.

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The growth of Bluetooth in other applications, outside the hearing care industry, is well documented (Figure 2). Furthermore, both Bluetooth integrated circuit technology and communications protocols continue to undergo considerable downsizing.

Figure 2

Figure 2

A new Ultra Low Power Working Group (ULP WG) has been formed within the Bluetooth Special Interest Group (SIG) to focus on creating ultra-low-power Bluetooth technology at the physical and link layers of the communication protocol.7 The physical layer refers to the Bluetooth radio and antenna, whereas the link layer refers to the wireless communication protocol used to transmit and receive Bluetooth packets and handle interference from other wireless devices and errors. This work should encourage the formulation of ultra-low-power Bluetooth-based personal area networks for medical applications.

In addition to Bluetooth itself, other related wireless protocols have begun to appear. One of these, Wibree—an abbreviation of Wi (for wireless) and bree (Old English for crossroad), hence Wireless at the Crossroad—is an ultra-low-power radio technology created for small devices that could be powered by small batteries like button cells with capacities similar to hearing aid batteries.

Wibree, developed principally by Nokia, has a lower data rate and consumes much less power than Bluetooth. However, a dual-mode Bluetooth-Wibree radio still has a communication speed of up to 1 million bits per second at a distance of 5–10 meters, quite adequate for audio applications. The lower power consumption holds great promise in overcoming concerns about the short battery life of earlier Bluetooth devices.

In June 2007, the Wibree forum was merged into the Bluetooth Special Interest Group (SIG) for the purpose of making Wibree part of a new ultra-low-power (ULP) Bluetooth specification. Since Wibree is now being supported by the major Bluetooth integrated circuit suppliers, most of the Bluetooth chips shipped by the end of 2008 will have dual-mode Bluetooth-Wibree capability, which could result in over 100 million Wibree-enabled cellular phones by the end of 2009.8

While Wibree is lower in average current consumption than Bluetooth, this is a result of having a low duty cycle, meaning that it is intended to be infrequently used for transmitting data or control functions, so the average current is kept relatively low. Therefore, for wireless hearing aid applications in which continuous audio must be transmitted, Wibree may not be a good solution.

Another Bluetooth spin-off, direct sequence spread spectrum wireless technology, holds a different type of promise. It has the capability of performing point-to-multi-point or broadcast (one to many) transmission, in contrast with present Bluetooth transmission, which is constrained to point-to-point applications. When this CDMA technology becomes available, it will open up applications for groups, with advantages over existing FM and Bluetooth protocols. Thus, this technology may find use in classrooms and public places in which the signal is broadcast simultaneously to many listeners with appropriate receivers.

In addition to the advent of Wibree and CDMA, Bluetooth itself is seeing important improvements. Since 2000, Cambridge Silicon Radio, the most used designer of Bluetooth chips, has progressed from BlueCore 1 to BlueCore 5. During that time both the size of the chip (Figure 3) and its power consumption have decreased markedly. A BlueCore 5 chip, which is about 4 x 4 mm, is similar in size to a typical hearing aid circuit and draws about 8 mA from a 1.8-volt power source while the Bluetooth portion is being utilized. When the Bluetooth functionality is idle, the current drawn is about 3 mA for the digital signal processor. Unfortunately, both of these current drain numbers far exceed the current consumption of most modern hearing aids.

Figure 3

Figure 3

Not only have size and power consumption decreased, but other processing and operational characteristics of the chip have improved. The items below represent a partial list for which continuous improvements are being made:

  • improved speed, ease, and consistency of pairing and connecting
  • elegant error-handling capability
  • broader bandwidth and full stereo capability
  • easy switching of input source and output mode
  • increased data rate
  • incorporation of conventional FM on Bluetooth chip

The essence of this technological progress is captured conceptually in Figure 3, showing a steady reduction in size and a simultaneous growth in product capability.

While Figure 3 shows that significant progress is being made in downsizing Bluetooth size, it doesn't mean that Bluetooth is now ready for use inside hearing aids. At this time, Bluetooth is still unable to be incorporated directly into all models of hearing aids because of the large space it occupies and the relatively high battery current it requires. That is not to say that Bluetooth will not have other mainstream applications that will continue to grow. Reductions in the size and power required by Bluetooth will continue to occur. Eventually, when these challenges have been solved, Bluetooth will evolve until it is suitable for use inside hearing aids.

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When Bluetooth products first appeared as assistive devices for use with hearing aids, they were accepted enthusiastically by a relatively small contingent of early adopters. These sophisticated users of technology are still benefiting from these Bluetooth devices, which allow them to hear without interference on a digital mobile phone or carry on conversations in a noisy car or restaurant. However, these products have not seen the growth experienced by other Bluetooth products outside of hearing care applications. They have not been accepted yet by the early majority because of the extra external devices required and user interface issues listed previously.

The greatest promise offered by recent and coming advances in Bluetooth is that some day the technology will be small enough and sufficiently low in its power demands that it can be fully incorporated into a wearable hearing aid. No additional gadgets will be needed. No relay around the neck, no inductive transducer, no module to translate the Bluetooth signal into a proprietary, and more expensive, wireless protocol. All you will need is a hearing aid. But it will also be more than a hearing aid.

The main uses of the coming Bluetooth devices will be the same as those identified at the outset: hearing on the telephone, including digital mobile phones, without wires or interference, and hearing well in a noisy room, the arch-nemesis of hearing aid wearers. A secondary benefit will be easier access to entertainment. The main difference is that the device providing these benefits will be considerably less intrusive than its predecessors. It will function more like an appliance; just turn it on, and it will do what it's intended to do. You won't need to be a member of the geek squad to use it.

When these promising developments come to fruition, who will be the adopters of the technology? Earlier we identified two potential early adopters. The first was the person with a moderate or greater hearing loss, the long-time user of BTEs, who has accepted the need for these rather visible devices and who is willing to adopt additional gadgetry to achieve the goals of hearing on the phone and in noise. The second potential group of early adopters consists of those people with borderline losses who have not yet moved to hearing aid use. They represent the typical market segment for a disruptive technology: those who are not yet part of the existing market.

The users of this coming technology will be drawn to a combined Bluetooth receiver and hearing aid by the fact that it will put them in touch with the world in a way that nothing else can. They can listen to their MP3 player, carry on a wireless telephone conversation, hear the television without turning the volume up, and hear the person across the table in the noisiest bar. Greater range will become available, enabling listening even in an auditorium or place of worship. Multi-user capabilities will allow use in classrooms or places of worship. Automatic recognition systems will recognize their Bluetooth receiver when they walk into the room and connect them to available signal sources. It is our prediction that the users of this technology will eventually consist of anyone who uses a hearing aid. The two devices will be one and the same.

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The authors express sincere gratitude to Randall Roberts for his helpful contributions of technical knowledge and graphical expertise to the preparation of this article.

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  • the comparatively few technologists (technology enthusiasts) who are intrigued with and pursue new technology aggressively before the launch of formal marketing campaigns
  • customers who forgive high prices, omissions in functionality, poor performance, just to see how the new technology works
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Early Adopters

  • visionaries (with a dream) who can match an emerging technology to a strategic opportunity
  • expect a discontinuity from existing ways to get a breakthrough, not just improvement
  • are not surprised by bugs in new products resulting from discontinuous technology
  • make buying decisions based on their own intuition, vision, and imagination; are easy to sell, but hard to please
  • their acceptance typically results in a lot of enthusiasm and publicity
  • their endorsement is not always a good reference for the next group—the early majority
  • sales to early adopters frequently represent an initial blip, not a ramp up
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Early Majority

  • customers who constitute about 1/3 of the total who are driven by a strong sense of practicality, are sensitive to price, like good deals, and are hard to win over
  • want to buy an enhancement or productivity improvement for existing established products/operations and do not want to disrupt their organizations
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Late Majority

  • practical like the early majority; also constituting about 1/3 of the total
  • accept the recommendations of the early majority
  • tend to buy from large, well established companies
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  • Skeptics, those who, for personal and economic reasons, don't want anything to do with new technology
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1. Technology Review: Nokia adds low-power technology for wireless watches, jewelry and toys to Bluetooth group, 2007 .
2. Yanz J: The future of wireless devices in hearing care. Hear Rev 2006;13(1):18–21.
3. BlueEar: BlueEar Assistive Listening System, 2004 ,
4. Hagedoorn J: Bluetooth enabled hearing aid. Patent application US2003/0045283, March 6, 2003.
5. Moore G: Crossing the Chasm. New York: Harper Business Essentials, 2002.
6. Christensen C: The Innovator's Dilemma. New York: Harper Business Essentials, 2003.
7. Foley M: Ultra low power Bluetooth technology and call for participation, Bluetooth Special Interest Group letter, July 16, 2007.
8. Hun N: An introduction to Wibree. Antenna Systems & Technology 2007;Jan-Feb:18–20.
© 2007 Lippincott Williams & Wilkins, Inc.