Trends in Audio Streaming for Hearing Aids and Hearing Aid Compatibility for Wireless Phones

A 10-year snapshot of the availability of telecoil and Bluetooth wireless technologies for hearing aid users drawn from HearingTracker data.

An increasingly important feature for hearing aids and cochlear implants is a means to connect directly and wirelessly to an outside sound source. For decades, this direct wireless connection could only be accomplished by using a telecoil built into the hearing device. Telecoils couple to external sound sources, such as telecoil-compatible telephones or large-area hearing loop systems like those found in some places of worship, movie theaters, meeting rooms and other venues.

Hearing Aid

Accessing a hearing loop with a telecoil-equipped hearing aid is as simple as changing listening programs through a hearing aid smartphone app or sometimes by simply pressing a button on your hearing aid.

More recently, Bluetooth for direct audio streaming between hearing aids and other audio devices has become available in many hearing devices. While all hearing devices have built-in microphones to pick up sound in the environment for processing and delivery to our ears, neither telecoil nor any direct Bluetooth audio streaming technology has been universally implemented for sound transmission.

This article provides a 10-year snapshot of the availability of telecoil and Bluetooth wireless technologies for hearing aid users. More specifically, it shows how Bluetooth technologies are becoming more widely employed in hearing aids, and why there is also good reason to believe a more universal wireless technology will be available soon.

What are telecoils and what defines Hearing Aid Compatibility (HAC)?

Telecoils are simple analog input devices that consist of a wire wound around a metal core. First developed in the 1940s, telecoils act as internal receivers that pick up magnetic signals.

Among telecoil-enabled hearing devices, the telecoil can be selected for use with the telecoil (T-Coil) feature setting for wireless hearing. Magnetic signals are transmitted by telephones, induction hearing loop systems, and neckloops that can be connected to the receiver of other assistive listening systems or electronic devices (e.g., computers, tablets, etc.). In hearing aids and cochlear implants, telecoil use is a proven way of addressing noisy and reverberant acoustic environments, as well as overcoming distance from the speaker or sound source—all factors that reduce speech understanding.

Hearing Loop Symbol

Telecoil coupling is fully interoperable across wireless phones regardless of operating system (e.g., iOS or Android); any telephone with a T-coil can work with any hearing aid that has a telecoil.

In the case of telephones, the Federal Communications Commission (FCC) requires that telephone handsets be compatible with hearing aids and cochlear implants. Technical standards are used to determine if a telephone handset meets the FCC hearing aid compatibility (HAC) requirements, which include telecoil coupling capability. HAC requirements have been in place since Congress passed the 1988 Hearing Aid Compatibility Act. Over time, these requirements have been extended beyond landline phones to include, in part, wireless phones, such as today’s smartphones.

Telecoil coupling is fully interoperable across wireless phones regardless of operating system because telecoils are a non-proprietary solution. Any telephone that has telecoil coupling capability can work with any hearing aid that has a telecoil. And any hearing aid that has a telecoil can work with any telephone that has telecoil coupling capability.

Although hearing aid compatibility has become synonymous with telecoil coupling, the HAC Act is technology agnostic. The law itself does not specify that the means for accomplishing compatibility between hearing aids and telephones must be accomplished using a telecoil; rather, it encourages the use of currently available technology, which at the time the law was enacted and until only recently, was limited to telecoil coupling. 

Bluetooth Low Energy (LE) for audio streaming in hearing aids: MFi and ASHA 

In the last ten years, the use of Bluetooth for direct audio streaming of voice calls or media from a wireless device (e.g., a smartphone) to a hearing device has become much more commonplace. Apple was the first wireless device manufacturer to implement direct Bluetooth-based audio streaming in their iOS handsets through their Made for iPhone (MFi) technology.

The key to supporting this advancement in hearing aids was to address their lower power requirements. Apple did this by using Bluetooth Low Energy (LE) technology. However, at the time, audio streaming was not supported by Bluetooth LE. Consequently, Apple developed a proprietary extension that would support this capability while also taking advantage of the reduced power consumption afforded by Bluetooth LE.

MFi hearing aids can use traditional means of coupling to both iOS and Android phones for voice calling, either acoustic coupling through the hearing aid’s microphone or inductive magnetic coupling if the hearing aid has a telecoil. However, due to MFi’s proprietary nature, MFi technology in hearing aids can only be used to couple with Apple iPhones; it cannot be used to provide Bluetooth audio streaming for voice calling to Android devices.

The first iPhone to support MFi hearing aids and the first MFi hearing aids came on the market at the end of 2013. All iPhones since that time support MFi hearing aids—and a growing number of hearing aids are MFi capable.

In 2019, Google introduced their Audio Streaming for Hearing Aids (ASHA) technology in phones using the Android operating system. Like Apple, the Google solution needed to utilize a proprietary extension to take advantage of the Bluetooth LE technology. For a hearing aid to be interoperable for voice calls with both iOS and Android phones using Bluetooth LE-based technology, manufacturers need to implement both solutions – MFi and ASHA – into their devices.

Improving hearing aid compatibility for smartphones and other wireless handsets

Currently, the Hearing Aid Compatibility (HAC) Task Force, a group of key stakeholders, is working to make recommendations to the FCC on HAC compliance for all wireless handsets.

The Alliance for Telecommunications Industry Solutions (ATIS) convenes this effort on behalf of these stakeholders, including the:

The Task Force is collecting data about current technical and market conditions involving wireless handsets and recent innovations in hearing improvement technology. The goal is to deliver recommendations to the FCC by the end of 2022 that could serve as the basis for future FCC rules in this area. Data of interest to the task force includes:

  1. What the current availability of telecoils is in hearing aids;
  2. What the current availability of Bluetooth audio streaming (either Bluetooth-LE based MFi and ASHA technologies or Bluetooth Classic technology) is in hearing aids, and
  3. How the availability of these various methods has changed over time. 

Wireless telecoil, MFi, and ASHA use in hearing aids over time: HearingTracker data

HearingTracker maintains a database that includes the main hearing aid brands and their technology levels from the major manufacturers. This data has been curated since 2008 and uses information from the specification sheets of hearing aid manufacturers to create a consumer tool for comparing selected hearing aids. 

While each year’s data is not exhaustive, inclusion criteria—based on market share and judgments of meaningfulness and interest to consumers—suggest that it does represent a reasonable sample of the hearing aid market (Table 1). The data primarily consists of RIC- and BTE-style hearing aids with some custom styles (ITE, ITC, CIC) which together constitute most hearing aid styles sold. 

Global Hearing Aid Manufacturing Groups 1200x675

Table 1. Global hearing aid manufacturing groups (Parent Groups) and the hearing aid brands included in this study.

For purposes of the task force, we looked at 10 years of data from 2012 through 2021 and a total of 806 hearing aids with release dates during that time. 

Bluetooth LE gaining popularity in hearing aids; Telecoils still prevalent

Among the major hearing aid manufacturers and their main brands found in the HearingTracker database, Low Energy (LE)-based Bluetooth as a direct audio coupling method for wireless phone calling has been steadily increasing in availability over the past 9 years since Apple’s MFi was introduced (Figure 1).

Telecoil And Bluetooth Le

Figure 1: The wireless streaming technologies (telecoil, MFi, and ASHA) used in hearing aid brands included in this 10-year study (2012-2021).

With the introduction of Android’s ASHA capability, its availability has grown quickly over the last 3 years and is always implemented alongside MFi, which means the availability of both solutions in hearing devices has also grown quickly. The inclusion of a telecoil in hearing aids over the last 10 years has somewhat declined. 

Another Bluetooth solution: Bluetooth Classic

Bluetooth solutions in hearing aids have not all used Bluetooth LE proprietary extensions for direct audio streaming with wireless phones. In 2018, Sonova launched a Bluetooth solution in its Phonak hearing aid brand that utilizes the Classic version of Bluetooth. Classic Bluetooth supports audio streaming but at a cost in terms of power requirements and audio latency compared to Bluetooth LE.

With the Sonova Bluetooth Classic approach, hearing aids are fully interoperable with both iOS and Android phones for audio streaming of voice calls or media and support for features like hands-free calling. Currently, other Sonova hearing aid brands such as Unitron and their Advanced Bionics cochlear implants utilize Bluetooth Classic.

The availability of direct audio coupling methods over time

By also considering hearing aids found in the HearingTracker database that implement the Bluetooth Classic solution, we can look at how all direct audio coupling methods available to consumers for wireless phone calling have changed over time in this sample (Figure 2).

Available Coupling Methods

Figure 2. The hearing aid coupling options and combinations (Mic Only, Mic+TCoil, Mic+Bluetooth, and Mic+TCoil+Bluetooth) available in hearing aid brands over the last 10 years. Bluetooth (BT) combines MFi, MFi plus ASHA, and Bluetooth Classic methods.

Hearing aids with only microphone coupling capabilities (Mic only) or microphone plus telecoil coupling capabilities (Mic+TCoil) have been declining in favor of devices that also include some form of Bluetooth coupling (i.e., MFi, MFi plus ASHA, or Bluetooth Classic). The hearing aids in the database that utilized Bluetooth Classic did not support MFi or ASHA. 

In the last two years (2020 and 2021), most hearing aids in the database included some form of Bluetooth coupling capability. About half of those also included telecoils.

Hearing aids generally remain on the market for approximately 5 years. Among hearing aids available in 2021 to consumers, the HearingTracker data from 2017 through 2021 suggest that:

  1. A little more than half (54%) of available hearing aids included telecoils, and
  2. More than three-quarters (80%) of available hearing aids were Bluetooth capable (i.e., either MFi, MFi plus ASHA or Bluetooth Classic).

Of those hearing aids that were Bluetooth capable:

  1. Almost two-thirds (61%) were MFi capable;
  2. Of the MFi capable hearing aids, about one-third (33%) were also ASHA capable, and
  3. Another 19% of hearing aids were Bluetooth Classic-only capable.

Consumers now have a variety of hearing aids available that afford multiple ways of coupling to the telephone and other sound sources they want to listen to in their environment. More choice provides greater flexibility in and opportunity for meeting their hearing needs. Availability does not necessarily directly translate into sales and utilization, so it would be helpful to understand more about those areas to get a better sense of consumer preference.

Bluetooth SIG: Toward a more universal solution for hearing aid wireless streaming

In the very near future, it is expected that hearing aid and cochlear implant manufacturers will begin to implement another option for wireless audio streaming. This new Bluetooth LE-based technology called Bluetooth LE-Audio will support direct audio streaming functionality to wireless phones and more. Work on this new standard began in 2014 with a memorandum of understanding between the European Hearing Instrument Manufacturers Association (EHIMA) and the Bluetooth Special Interest Group (SIG).

The Bluetooth SIG introduced the Bluetooth LE-Audio standard in 2020 and recently (June 7, 2022) released the Hearing Access Profile (HAP) and Service (HAS). Bluetooth LE-Audio and its HAP and HAS profiles are non-proprietary solutions, inspired by their MFi and ASHA precursors, that will provide interoperability with both iOS and Android devices.

The new Bluetooth LE-Audio solution will have the same telephone and media audio capabilities as Bluetooth Classic, while also performing better in terms of power management, audio latency and providing advanced settings configuration, among other things. LE-Audio also enables Auracast for broadcast audio, another Bluetooth technology on the horizon.

Bluetooth Auracast 1200x675

Auracast is designed to enable an audio transmitter, such as a smartphone, laptop, television, or public address (PA) system, to broadcast audio to an unlimited number of nearby Bluetooth audio receivers—including hearing aids, cochlear implants, earbuds, and similar Auracast-enabled devices.

Over time, it's likely that the new Bluetooth LE-Audio solution for direct wireless audio streaming will become ubiquitous and universally used in hearing devices and wireless phones, as well as other consumer electronics devices, such as televisions, computers, and more. Over the next several years, we can look forward to another snapshot of the landscape regarding hearing aid coupling options to wireless phones and other sound sources as HearingTracker continues its database curation.


Abram Bailey, CEO of HearingTracker, generously provided the HearingTracker data to the HAC Task Force for this analysis to inform the task force’s work. Members of the HAC Task Force and Karl Strom, editor in chief of HearingTracker, reviewed and provided many helpful comments to the author.