How Phonak Achieved Universal Bluetooth Hearing Aid Connectivity
Integrating Bluetooth Classic on Sonova SWORDTM Chip-enabled Wireless Streaming Breakthrough
Phonak took many people by surprise in November 2018 when it launched Marvel™, the first hearing aid capable of streaming audio—in stereo—directly to and from any Bluetooth®-enabled audio devices. Previously, no other hearing aid manufacturer had solved the technical challenges of universal Bluetooth connectivity.
Phonak promotional video describes Marvel benefits including universal Bluetooth hearing aid connectivity. Closed captions are available on this video. If you are using a mobile phone, please enable captions by clicking on the three small dots.
Accessibility moves beyond Apple
Before Phonak introduced Marvel, only iPhone users had exclusive access to hassle-free direct stereo streaming. Android users, on the other hand, had to purchase and tote around separate streaming accessories to access wireless audio, from their phones. With Android accounting for 86% of the global smartphone market¹, that left a clear unmet need. And for the others—the Blackberry and Windows-phone users—well, most had given up entirely on ever having a wireless streaming option for their hearing aids.
To address this accessibility challenge, Phonak tasked a multi-disciplinary technical team of engineers and product designers to develop a truly universal wireless audio solution. Phonak wanted to ensure that all cell phone users — iPhone, Android, and otherwise — would have the same audio streaming experience, regardless of the type of phones in their pockets.
The Phonak tech team was successful in developing a universal Bluetooth solution, and they were way ahead of the curve. But, how did they do it? Here is the story behind the technologies that came together to deliver one of the most important recent breakthroughs in hearing aid functionality.
Technical challenges to integrating Bluetooth Classic with hearing aids
There were two main challenges the Phonak engineering team had to overcome: (1) Power consumption and (2) Streaming to two ears. In the past, these seemingly impossible challenges led other hearing aid manufacturers to use Apple’s proprietary Bluetooth Low Energy Audio (LEA) technology.
1. Power consumption
It is often noted that Bluetooth Classic is "power hungry." Other hearing aid manufacturers chose not to use it as a technology for streaming audio because it consumes significantly more power than the Made for iPhone technology. The hardware required for Bluetooth transmission can be designed to fit into a hearing aid. But the power requirements, unless addressed properly, would limit the battery life of a zinc-air battery below acceptable levels².
2. Streaming to two ears
Bluetooth Classic is capable of streaming stable, high-quality stereo audio. But it supports only one connection for streaming. In order to stream the same audio to both hearing aids, two connections are required. To solve that problem, the team had to develop innovative shortcuts which, if not implemented properly, could have resulted in a significant imbalance in power consumption between the two hearing aids.
Phonak Marvel hearing aid wearer Jill Quick describes how Marvel Bluetooth connectivity helps her through her days. Closed captions are available on this video. If you are using a mobile phone, please enable captions by clicking on the three small dots.
Solving the Bluetooth Classic challenges with the SWORD chipset
To solve the challenges of battery consumption and binaural streaming of music and phone calls, Phonak developed the third generation of the SWORD (Sonova Wireless One Radio Digital) wireless chip. SWORD not only utilizes Bluetooth Classic but also supports Bluetooth LE and other protocols. Its combination of features, all integrated on a single hearing aid chip, overcomes the battery life and audio streaming limitations of earlier chipsets.
For example, the SWORD chip has improved radio sensitivity, which enables it to handle the power demands of Bluetooth Classic. It reduces power consumption while maintaining excellent link distance and link stability. And to overcome the Bluetooth limitation of streaming to one ear only, the Phonak team developed a dedicated algorithm that extends the Bluetooth capabilities to allow streaming to both ears.
Miniaturization of the wireless chip
Miniaturization of technology is one important key to unlocking universal wireless connectivity and enabling complex algorithms without increasing the power consumption. In 1965, Gordon Moore observed that “processor speeds, or overall processing power for computers, will double every two years”³. This empirical statement became famously known as “Moore’s Law," which was responsible for computers becoming faster, smaller and less expensive by orders of magnitude over the years.
The SWORD chip from Sonova integrates all the protocols required for universal Bluetooth connectivity in Phonak Marvel hearing aids.
Moore's Law can also be applied to wireless digital hearing aid technology. As the sizes of chip structures get smaller and processing speeds increase, power consumption can be reduced. When transistors on the chip are smaller and more tightly packed, electrons don't have to travel so far when moving between them, saving both time and energy⁴. The smaller the transistor size, the more transistors can be added with more sophisticated features—without increasing battery drain.
The Phonak SWORD is an ultra-small, ultra-low-power chip. The structure includes 42 million transistors placed on a 6.8 mm2 size chip. Using 40 nm CMOS technology, SWORD is the only wireless chip capable of combining one radio chip with one antenna to power all applications. It is currently one of the lowest-power-consuming solutions for hearing aid applications.
SWORD offers the processing power required for wireless binaural audio streaming using Bluetooth Classic. At the same time, it provides proprietary audio links for ear-to-ear streaming, enabling unique functions such as the Phonak Binaural VoiceStream Technology™. These connections use the same antenna, allowing further reductions in the size of the hearing aid.
Binaural audio streaming is optimized for external devices using an extension of Bluetooth Classic. With a new wireless antenna design optimized for ear-to-ear and off-body performance, SWORD is capable of transmitting audio around the head, providing more stable Bluetooth connections.
Figure 1 shows the benchmarking of SWORD against other similar wireless chip technologies found in consumer wireless earbuds and 2.4 GHz Made for iPhone hearing aids from other manufacturers.
Figure 1: A comparison of the SWORD chip with other Bluetooth solutions. SWORD is by far the best in class in terms of size, area, smallest technology, current consumption, and the number of protocols.
When comparing chip size and technology, Sword far outperforms both wireless consumer earbuds and Made for iPhone hearing aids. It is the only chip that is able to simultaneously use multiple protocols like Bluetooth Classic, Bluetooth LE and several proprietary protocols. SWORD current consumption is comparable to the competitor Made for iPhone hearing aids but far outperforms the consumer wireless earbuds.
Radio sensitivity and antenna design
The sensitivity of the radio chip and of the antenna are also important in optimizing power consumption. As the human body absorbs 2.4 GHz, it is very difficult for the signal to move around the body. But a well-designed radio antenna can help reduce power consumption, especially on the transmitter side, without decreasing the link distance and stability.
Hearing aids have traditionally relied on an inductive link requiring duplication of radio and antenna. SWORD was designed to provide a sensitivity enabling binaural audio transmission. The radio antenna of SWORD was designed and optimized to allow stable back-and-forth streaming of external audio signals as well as communication around the head. It has the advantage of not being sensitive to the body proximity and thus does not suffer from a degraded performance when worn on the ear. (The collective experience obtained from the introduction of Phonak Roger™ technology in 2013 was of great benefit when developing the radio antenna.)
SWORD is the only wireless chip available which requires just one radio antenna to support short link distances for on-body ear-to-ear streaming with Binaural VoiceStream Technology, off-body long link distances like Bluetooth Classic and Bluetooth LE, and multiple protocols that are used for every day listening (figure 2).
Figure 2: Multiple protocols are integrated into the SWORD chip.
Power management and battery consumption
SWORD was designed for low power consumption. Its power management system includes voltage converters, which minimize the current consumed by Phonak hearing aids when using Bluetooth Classic to its full effect, lessening battery consumption. This new power management system ensures that clients will experience comparable hearing aid battery time when streaming music or phone calls, compared to Made for iPhone hearing aids.
Without all these improvements, integration of Bluetooth Classic would result in significant drawbacks in power consumption. That is one of the reasons manufacturers of Made for iPhone hearing aids opted to use the proprietary Apple Bluetooth LEA technology instead. With the Apple protocols, hearing aids can support two connections for binaural audio streaming. But the disadvantages of these solutions include limited connectivity to only Apple iPhones and iPads, no hands-free phone calls, and no connectivity to other devices such as Apple computers.
Figures 3 and 4 show a comparison of the peak and average current when streaming audio and phone calls, for Marvel hearing aids and two competitive Made for iPhone Receiver In Canal (RIC) hearing aids.
Figure 3: Peak and average current comparison of music streaming from RIC hearing aids that use 2.4GHz frequency technology. For comparable results, the measurements were performed without a receiver.
Figure 4: Peak and average current comparison of phone call streaming from RIC hearing aids that use 2.4GHz frequency technology. For comparable results the measurements were performed without a receiver.
"Peak current" indicates how much current is drawn when the radio is turned on and denotes the efficiency of the chip. For zinc-air batteries, peak current is important, as these batteries can only take in a limited amount of air to produce electricity, thus they can only provide a certain maximum current. If this amount is exceeded (which depends on the battery (10, 312, 13, 675), the battery voltage decreases and the hearing aid shuts down, at least temporarily. This effect is called "oxygen starvation," as the battery cannot breathe sufficiently anymore.
The effect becomes more pronounced towards the end of the battery life and can prematurely end the life of a zinc-air battery, even though it has still the capacity to deliver lower currents. The aim is to reduce the peak current consumption in a device. This is not relevant for rechargeable Lithium-ion batteries, which can deliver much higher peak currents and don’t require air.
Apart from the oxygen starvation effect, every battery has a certain capacity. The battery can also last longer if the hearing aid draws a lower average current. During music streaming and phone calls, both Bluetooth Classic and Bluetooth LE radios are turned on and off at a regular interval. This results in a lower average current consumption. This effect is of course relevant for all kinds of batteries, including Zinc air and Lithium-ion.
The graphs in Figures 3 and 4 show that SWORD is capable of using Bluetooth Classic to stream audio in hearing aids without suffering high peak (and average) current consumption. The peak and average current response of SWORD when using Bluetooth Classic for streaming is very close to the two Made for iPhone hearing aids that use the energy-efficient Bluetooth LEA to save on power consumption. This refutes the argument against using Bluetooth Classic for audio or phone streaming in hearing aids.
Experience with Lithium-ion rechargeable solutions and analysis of long-term performance data enabled Phonak to further optimize the 2nd generation rechargeable solution. Based on internal data analysis, 98% of Phonak Audéo™ B-R wearers (n=12’239) utilize their rechargeable hearing aids for less than 17 hours per day.
Datalogging data from more than 192,000 clients (wearing Phonak Belong) showed an average daily wearing time of 10.4 hours. Using this information, Phonak defined the battery life time of the rechargeable hearing aids as 16 hours usage per day and consisting of:
- 8 hours AutoSense OS™ 3.0 and Binaural VoiceStream Technology™ (50%)
- 4 hours Bluetooth streaming, phone call (HFP) and media (A2DP) (25%)
- 4 hours TV usage with TV Connector (AirStream™ technology) (25%)
Figure 5: The calculated battery consumption when using Audéo Marvel hearing aids for audio streaming 100% of the time, a mix of acoustic listening and audio streaming, and acoustic listening 100% of the time. Battery life varies by use, configuration, and other factors; actual results will vary.
Figure 5 shows the calculated battery consumption is based on preliminary tests, conducted by Phonak using preproduction Audéo™ Marvel. Battery life varies by use, configuration and other factors; actual results will vary. The test sequence includes an acoustic stimulation with 16 hours “On” time/day. The test includes multiple, automatically activated streaming sequences with a total of 8 hours wireless streaming time.
The hearing aids were fit with a typical, severe-to-profound hearing loss (N5) and P Receivers. Average loudness level in the box is 65-75 dB (variation of soft/moderate office environment, loud/heavy traffic and restaurant environment). This test has an extension for audio recording of the outputs of the receivers, to record the warning and notification signals.
Using the same conditions listed above, Audéo Marvel hearing aids with a size 13 zinc-air battery were found to provide 100 hours of listening enjoyment including streaming (figure 6).
Figure 6: The average battery time of Phonak Audéo Marvel hearing aids that use rechargeable, 312 zinc-air and 13 zinc-air batteries.
Comparing Audéo Marvel rechargeable hearing aids to wireless earbuds, both using Lithium-ion rechargeable batteries, Audéo Marvel hearing aids can be used for 11 hours of phone calls or music streaming, while wireless earbuds, which also use Bluetooth Classic, provide only up to 5 hours of listening time and 2 hours of talk time on a single charge⁵.
Phonak has achieved a breakthrough with SWORD technology using Bluetooth Classic. By miniaturizing the wireless chip as well as improving the radio sensitivity and antenna design, only Phonak currently harnesses the benefits of using Bluetooth Classic to stream audio and hands-free phone calls binaurally to hearing aids without jeopardizing power consumption. This is thanks to SWORD and its super small, power-efficient 40 nm chip technology.
The latest generation of Phonak hearing aids are able to utilize multiple protocols including:
- Bluetooth Classic for binaural phone connectivity and music streaming.
- Bluetooth LE for remote controls and wireless hearing aid fitting.
- Proprietary protocols for connecting to Roger technology, streaming from the TV Connector and binaural ear to ear data and audio exchange with Binaural VoiceStream Technology.
All this is possible with a battery consumption that is similar to or better than some Made for iPhone hearing aids that use a proprietary Bluetooth LE protocol and can only stream directly to an iPhone or iPad device.
Given the high global market share of Android and iOS smartphones, SWORD can connect to a majority of devices and offer clients a full day of binaural music streaming and phone calls without having to worry about battery consumption.
Click here for more information on Phonak Marvel and its Bluetooth Classic connectivity.
Phonak promotional video provides overview of Marvel hearing aid technologies, including universal Bluetooth connectivity.
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- Galster, J. (2014 November/December). Making sense of modern wireless hearing aid technologies. Ent and audiology news, 23, 5.
- Moore, G.E. (1965) Cramming More Components onto Integrated Circuits. Electronics, 38, 8.
- Weste, N. & Harris, D. (2011). CMOS VLSI Design: A circuits and systems perspective, (4th ed.). Boston, MA: Addison-Wesley.
- Charge your AirPods with charging case and learn about battery life. (2018). Retrieved from https://support.apple.com/en-us/HT207012, accessed February 27th, 2019.
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