Sound Science: Apple Details How It Turned AirPods Into Capable Hearing Aids

Apple gave a behind-the-scenes look into how the company went about adding a hearing aid feature to its AirPods Pro 2 earbuds recently. The science behind the feature was fine-tuned at Apple’s state-of-the-art Audio Lab in Cupertino, California, where acoustic engineers conducted user studies in various listening rooms.

The Cupertino-based company revealed the new feature during its “Glow Up” event last month, while later confirming its AirPods Pro 2 earbuds had indeed received FDA approval to be used as hearing aids. The FDA approval meant the AirPods Pro 2 earbuds would also be the first over-the-counter hearing aid software device to be made available. Now, Apple wants everyone to know a little bit about the science that went into the new and innovative hearing aid feature.

The new software, which is available now, is an end-to-end experience aimed at helping users minimize exposure to loud environmental noise with Hearing Protection, track hearing with an at-home Hearing Test, and provide assistance for perceived mild to moderate hearing loss using AirPods Pro as a clinical-grade Hearing Aid.

Shelly Chadha, M.D., of the World Health Organization, remarked, “According to the World Health Organization, approximately 1.5 billion people around the world are living with hearing loss. ‘Hearing loss affects individuals in every region and country, yet often goes unrecognized. Hearing is a core component of communication for so many and is an important factor for health and wellbeing.’”

According to Apple, every person’s hearing is different, so the company created an “innovative, end-to-end hearing health experience” that can address the variability in ways that are simple to use, and adaptable to a wide range of needs. With this in mind, engineers used highly specialized spaces across the Audio Lab to help develop the feature.

“From the quietest sounds we can hear for the Hearing Test feature, to speech in noisy restaurants for the Hearing Aid feature, and even concert levels for Hearing Protection, we can bring the real world into our acoustics facilities with playback of calibrated soundscapes from all over the world, or take accurate acoustic measurements at the touch of a button,” explained Kuba Mazur, Apple’s hearing health lead engineer within Acoustics Engineering.

One space Apple used was the Longwave anechoic chamber, which was built on a separate foundation that uses springs to isolate it from the rest of the lab. This allows for accurate sound measurements with no noise or vibration disturbances. The chamber also includes a loudspeaker and microphone arc that can measure head-related transfer functions. The chamber’s unique setup makes it perfect for testing applications which apply to AirPods, iPhone, and HomePod development.

Apple stated that on the other side of the Audio Lab, the Fantasia Lab uses a spherical array of 50 loudspeakers to simulate hundreds of real-world scenes, such as a loud shopping mall, busy street, or travel on an airplane, all in a “tightly controlled, evenly distributed sound field.”

In order to fine tune and validate the Hearing Aid feature, Apple implemented a broad demographic of study participants with a wide range of hearing levels, and placed them in the controlled environment to complete a speech-in-noise test. Apple commented the test comprised a participant sitting in a chair in the middle of the space while a complex sound scene, such as a noisy restaurant, played. The participant then had to repeat the words of a single speaker that was mixed in with the other sounds and voices.

In addition to all the above, Apple added it used three clinical-grade audiometric booths, the type patients might encounter during a hearing test in a clinician’s office. The engineering team worked with audiologists in the booths in order to conduct thousands of clinical-grade audiometry tests and software-based hearing tests before moving the new Hearing Test feature into clinical validation studies.

“The fact that people can walk around wearing their AirPods, that they can protect their hearing at concerts and get insights on their hearing health using these features over time — AirPods are doing what each person wants or needs them to do,” remarked Mazur. “They’re truly the interface to the ear.”

It's a neat inside look at the sound science that went into turning a set of earbuds into a viable hearing aid. Kudos to Apple for sharing.

You can find the AirPods Pro 2 for $244.99 on Amazon.