As the baby boomer generation grows older, more people are relying on portable medical technology to meet their healthcare needs and improve their well-being. Today, about 47% of adults over 75 are believed to suffer hearing loss in one or both ears. Other threats to hearing, such as noise or health problems, can affect people of any age. In fact, 12.5% of 6-19 year olds have permanent hearing damage due to excessive noise exposure.
While the hearing aid market is growing annually at 6-8 % CAGR (figure 1), potential growth remains much higher. Of those who could benefit from a hearing aid, shockingly few (approximately 4%) will actually purchase a hearing aid, believed to be influenced by the cost of the device and the associated negative stigma of old age. Though hearing aids offer a simple solution to an irritating problem, many patients will only revert to wearing a hearing aid if absolutely necessary.
Figure 1: Hearing aid market growth (HIA)
Today, advanced new features are being implemented in hearing aids to dramatically improve functionality, ultimately helping to make the user experience more enjoyable and thus increase adoption.
More Freedom with Wireless
As with many other wearables, wireless connectivity is quickly becoming more commonplace, instead of a feature found only on high-end hearing aids. Wireless technology makes it much easier for users to control their device, so making it available on a larger scale is critical.
Still today, making adjustments (e.g. volume control, program selection, etc.) on a hearing aid can be challenging. Users can make adjustments manually by selecting one or two small buttons on the device. Some may be able to do this while it is still on the ear, but others may have to remove it beforehand. Another option requires using a dedicated manufacturer-specific remote control, or a relay device (a larger unit typically worn around the neck). Most hearing aids available today don’t possess the ability to communicate directly with smartphones, so this additional unit is needed in order to convert the proprietary radio link hearing aids use into a standard Bluetooth® link smartphones can understand.
Since many people already carry and use smartphones, solely using it to communicate with and control the user’s hearing aids has by far the most appeal. Adding to its ease-of-use, custom smartphone applications feature intuitive icons and touch controls which are friendly for all levels of technical understanding. For hearing aids, these apps allow users to easily check their device’s battery levels, and optimize program or volume control settings of left and right hearing aids individually. Other features can include alerts to incoming texts or phone calls, or GPS tracking to help locate a misplaced hearing aid.
Using Bluetooth Low Energy (BLE) wireless technology, audio can be streamed directly to the hearing aid from an external source such as a sound system or a television equipped with an ancillary device. This can provide a more immersive entertainment experience for the wearer, with better audio quality. This technology can provide the opportunity to deliver better and more discrete user experiences for hearing-aid wearers. However, given the potential impact BLE can impose on power consumption and system size, it is something that is difficult to implement in miniature hearing aids.
Greater Design Challenges
Designers looking to enhance the functionality of hearing aids face extreme space constraints imposed by the more popular, discrete styles. Up to 80% of hearing aids currently in use are Behind-The-Ear (BTE) types (figure 2), usually an all-in-one design or with a remote receiver that is worn inserted in the ear canal. In-The -Ear (ITE) types make up about 20% of the market, in full or fractional shell sizes or miniature sizes designed to be inserted fully into the ear canal.
Figure 2: Today’s hearing aids are most commonly worn behind the ear
Within any of these form factors, the hearing aid designer must arrange the receiver, the battery and associated circuitry, user controls for volume adjustment and program switching, and the audio digital signal processor (DSP) and associated peripherals including memory and now a Bluetooth radio transceiver. One or more microphones are usually needed, to enable background-noise cancellation and directional sound pick-up (figure 3).
Figure 3: The typical hearing aid shell imposes tight space constraints
Overcoming the Barriers
System-in-Package (SiP) solutions can help overcome the space limitations of miniature devices by integrating several components into a single solution. ON Semiconductor recently revealed Ezairo 7150 SL, a wireless-enabled audio processing hybrid module which can easily be integrated into a standard BTE hearing aid shell.
Based on the programmable Ezairo 7100 digital signal processing (DSP) platform, the miniature hybrid module features a high-precision quad-core architecture. Ezairo 7150 SL provides multi-protocol wireless support, is optimized for 2.4 GHz license-free radio bands, and is compatible with BLE as well as custom protocol variants to deliver ultra-low-power stereo audio streams. To store important hearing aid parameters, Ezairo 7150 SL provides 2 Mb of non-volatile memory (EEPROM).
ON Semiconductor has produced a complete reference design of an Ezairo 7150-SL based BTE hearing aid, including the hybrid module, required passive components, and 2.4 GHz radio antenna to help designers develop and refine their own device. The reference design is comprised of fully- assembled hardware (figure 4), a sample Android application, and firmware for stereo audio streaming via a remote dongle and Control over BLE.
Figure 4: The reference design, with BTE shell, flex circuit, and antenna to accelerate project development
Multi-protocol wireless support enables advanced hearing aid features such as Control over Bluetooth Low Energy (CoBLE) using a smartphone or tablet, and audio streaming via a remote dongle that plugs into the standard audio output jack of the source equipment. The audio streaming protocol uses a proprietary low-latency radio link that consumes very little power (only about 4-5 mA off a standard Zinc-Air hearing aid battery).
The stereo audio streaming feature allows users to hear audio from any external source like televisions or car radios through the use of a small transmitter dongle. The dongle can also operate in remote microphone mode, further enhancing the user’s listening experience in challenging situations, like noisy environments or class rooms where the speaker might be far away.
The advanced features of modern hearing aids, especially wireless connectivity, pose serious new challenges to system-level design. With its high degree of integration, Ezairo 7150 SL promises greater performance, ease of use, reliability and ultimately, convenience for wearers of the device it enables.
Conclusion
Advanced features have the potential to revolutionise quality of life for wearers of hearing aids. Physical space constraints have been a key factor in limiting progress, but sophisticated integration techniques have now helped to enable wireless connectivity, such as Control over BLE and low-latency audio streaming, without the need for bulky relay devices. These features now set the scene for dramatic improvements to the end-user experience, helping to transform hearing aids from a device someone needs to use into one they’ll want to use.
