Breaking It Down | MFI Hearing Aids

By Jenny Groth

Until now, it has not been feasible to implement Bluetooth directly in hearing aids mainly due to power constraints, thus necessitating a wireless accessory for any communication with cell phones or smart devices. However, Bluetooth version 4.0 includes a low energy feature which meets the power constraints of hearing aids. Branded by the Bluetooth SIG (Special Interest Group) as “Bluetooth Smart,” this technology is a “power-friendly” version of the open Bluetooth wireless standard and has become popular particularly for monitoring devices like heart rate monitors and fitness trackers.

The availability of the low energy Bluetooth feature has made MFi hearing aids possible. An MFi hearing aid connects wirelessly to iOS devices without any additional hardware. According to Apple, “these hearing aids deliver a power-efficient, high-quality digital audio experience” and also allow users to manage their hearing aids from their iPhone devices.

A major part of the challenge of developing MFi hearing aids is mastery of robust radio frequency transmission at 2.4 GHz. Because its digital wireless hearing aid system was already based on radio frequency transmission at 2.4 GHz rather than the more common near-field magnetic induction (NFMI), ReSound was in a favorable position to develop an MFi hearing aid – the ReSound LiNX – relatively quickly.

So what can MFi hearing aids do? One of the most attractive features of MFi is audio streaming in high quality stereo. Any type of audio played from an iOS device can be streamed to MFi hearing aids, including music, podcasts, games, FaceTime calls, Netflix or YouTube videos just to name a few. While all of these uses certainly can add to the enjoyment and utility of using an Apple device, perhaps the most significant benefit is the streaming of phone calls to the hearing aids. Phone use is made difficult by the absence of visual cues, inappropriate or inadequate coupling to the phone and the presence of background noise. Not surprisingly, many hearing aid users feel they are unsuccessful on the phone.

Receiving the phone signal directly from the phone to the hearing aids with no intermediate accessory provides an obvious benefit in terms of convenience to the user. In addition, it has been established that a bilateral wireless signal optimizes benefit for hearing on the phone¹. A recent study of the benefit of different phone options including MFi reinforced this finding, but also suggests that MFi may provide additional benefit compared to streaming the phone signal via a wireless accessory with conventional Bluetooth². In this study, listeners were administered an adaptive speech-in-noise test with the speech presented unilaterally in four different telephone conditions:

1. Using the hearing aid microphone (“Acoustic Phone”)
2. Using the hearing aid telecoil (“Telecoil Phone”)
3. Streaming the phone signal via Bluetooth through a wireless hearing aid accessory (“Phone Clip+”)
4. Streaming the phone signal directly from the iPhone (“ReSound LiNX MFi”)

Performance in all wireless conditions exceeded the “Acoustic Phone” condition. The average SRT scores in dB for the four test conditions including 95% confidence intervals are shown.  All conditions are unilateral, with the phone signal in only one ear. The authors also noted the greater variability for the “Acoustic Phone” and “Telecoil Phone” conditions than the two digital wireless conditions, which they attributed to individual difficulties in placing and maintaining the telephone correctly for signal reception. As a result they predict more reliable benefit with the digital wireless solutions. What is also striking about these results is that the MFi condition was significantly better than either the “Telecoil Phone” or “Phone Clip+” conditions. This was in contrast to the expectation that the two digital wireless phone solutions would yield equivalent results. The authors speculate that this may be related to a decline in signal quality caused by the extra link needed when using a Bluetooth-based hearing aid accessory (phone-to-accessory-to-hearing aids). As mentioned, MFi also gives users the opportunity to manage their hearing aids from the iOS devices. In the case of the

ReSound LiNX, the ReSound Smart™ app enables this functionality. First of all, the ReSound Smart app serves as a remote control for the hearing instruments. Users can change programs, adjust volume and choose the input to the hearing aids. One adjustment type allowed by the ReSound Smart app that typically is not available to hearing aid users is an adjustment of treble and bass. This can be particularly useful for specific listening situations, such as music listening. Additionally, this app offers the capability to associate specific hearing instrument settings including the listening program, volume and treble/bass adjustments with a geographical location. This functionality is called “geo-tagging.” Finally, a “find my hearing aid” feature can help locate a misplaced device, and tutorials provide usage and troubleshooting advice that is easily accessible.

This content was originally published on Aubankaitis.com on May 7, 2014.

References:

1. Picou EM, Ricketts TA. Comparison of wireless and acoustic hearing aid-based telephone listening strategies. Ear & Hearing. 2011; 32(2): 209-220.
2. Nesgaard Pedersen J, Kirkwood B. Speech Intelligibility Benefits of Assisted Telephone Listening Methods. In press. 2014.

© 2014 The GN ReSound Group, all rights reserved. Apple, iPhone, iPad and iPod touch are trademarks of Apple Inc, registered in the U.S. and other countries. Bluetooth is a trademark of Bluetooth SIG, Inc.