Newborn screening in the United States routinely checks every baby, within the first one to two days of birth, to provide critically important information about the child’s health. There are three parts to a routine newborn screening: blood test, heart test, and hearing test. The hearing test, based on otoacoustic emissions (OAEs), provides information about the function of the outer hair cells of the cochlea. The test is very important (roughly 5.3% of the world’s population suffers from disabling hearing loss) but very expensive. Therefore, the screening is typically not available in low- or middle-income countries.

Now, a team led by researchers at the University of Washington (UW) has created a new hearing screening system that uses a smartphone and low-cost earbuds. The system costs about $10 dollars.

The earbuds are connected as shown here to a probe that can be placed in the patient’s ear. [Raymond Smith/University of Washington]
The team tested their device with 114 patients, including 52 babies up to six months old. The researchers also tested the device on pediatric patients with known hearing loss. Their tool (which detected hearing loss with 100% sensitivity and 88.9% specificity) performed as well as the commercial device. It correctly identified all patients with hearing loss.

This work is published in Nature Biomedical Engineering in the paper, “An off-the-shelf otoacoustic-emission probe for hearing screening via a smartphone.

“There is a huge amount of health inequity in the world. I grew up in a country where there was no hearing screening available, in part because the screening device itself is pretty expensive,” said Shyam Gollakota, PhD, professor in the Paul G. Allen School of Computer Science & Engineering at UW. “The project here is to leverage the ubiquity of mobile devices people across the world already have—smartphones and $2 to $3 earbuds—to make newborn hearing screening something that’s accessible to all without sacrificing quality.”

Because babies can’t tell doctors whether they can hear a given sound, hearing tests rely on the mechanics of the ear. For the current test, doctors send two different tones into the ear at the same time. Based on those tones, the hair cells in the ear vibrate and create a third tone, which is what the doctors are listening for.

“When an external sound is played, hair cells in the inner ear move and vibrate. The result is a very quiet sound that our instruments can pick up,” said Randall Bly, MD, associate professor of otolaryngology-head and neck surgery at the UW School of Medicine. “This screening is very sensitive, meaning that if there is a concern about a patient’s hearing, they will be referred for a more thorough evaluation with a specialist.”

The earbuds are connected to a microphone in a probe (shown here in blue) that can be placed in the patient’s ear. [Raymond Smith/University of Washington]
One reason the commercial device is expensive is that its speaker has been designed to play the two tones without any interference. The UW researchers found that they could use affordable earbuds—where each earbud plays one of the two tones—instead. The earbuds are connected to a microphone in a probe that can be placed in the patient’s ear. The microphone records any sounds from the ear and sends them to a smartphone for processing.

“As you can imagine, these sounds that are coming out from the ear are very soft, and sometimes it’s hard to hear them over noise in the environment or if the patient is moving their head,” said Justin Chan, a PhD student in the Gollakota lab. “We designed algorithms on the phone that help us detect the signal even with all that background noise. These algorithms can run in real-time on any smartphone and do not require the latest smartphone models.”

The researchers tested their device at three hearing clinics in the Puget Sound area in Washington. For each test, they tested four different frequencies, which is typical for these types of hearing screenings. Participants ranged in age from a few weeks to 20 years old.

Now the team is working with collaborators to use this tool as part of a newborn hearing screening project in Kenya. The researchers teamed up with a group from the UW global health department, the University of Nairobi, and the Kenya Ministry of Health to create the project, “Toward Universal Newborn and Early Childhood Hearing Screening in Kenya,” or TUNE.

Here, lead researcher Justin Chan, a UW doctoral student in the Paul G. Allen School of Computer Science & Engineering, uses the device to test a child’s hearing in Kenya. [Nada Ali/University of Washington]
“Right now, this is a prototype that we created. The next challenge is really scaling this up and then working with local experts in each country who are the most familiar with the particular challenges in each situation,” Chan said. “We have an opportunity to really have an impact on global health, especially for newborn hearing. I think it’s pretty gratifying to know that the research we do can help to directly solve real problems.”

To do that, Chan co-founded (with Bly and Gollakota) Wavely Diagnostics. The company plans to leverage the lab’s research to make pediatric healthcare more accessible.

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