The Scale of the Problem

According to the World Health Organization, more than 430 million people worldwide currently live with disabling hearing loss — defined as a threshold above 35 decibels in the better-hearing ear. By 2050, this number is projected to exceed 700 million, roughly one in every ten people on the planet. (WHO Fact Sheet: Deafness and Hearing Loss, 2024)

The burden is not evenly distributed. Nearly 80% of people with disabling hearing loss live in low- and middle-income countries, where access to audiologists, hearing aids, and follow-up care remains severely limited. Traditional hearing aids cost between $1,000 and $7,000 per pair in developed markets, and are often entirely out of reach elsewhere.

Unaddressed hearing loss carries an estimated annual economic cost of over $980 billion internationally — in healthcare, lost productivity, educational support, and social care. (WHO World Report on Hearing, 2021)

Who Is Most Affected?

Hearing loss increases sharply with age. Among people over 60 years old, more than 25% experience disabling hearing loss. For those over 75, the figure rises above 50%. (WHO, 2024)

But age is not the only factor. Occupational and recreational noise exposure is one of the leading preventable causes of hearing loss among working-age adults. Approximately 1.1 billion young people globally are at risk from unsafe listening practices, including headphone use at high volumes.

In children, around 60% of hearing loss cases stem from avoidable causes — vaccine-preventable infections, otitis media, and birth complications — making early detection particularly important.

The Treatment Gap

Despite the scale of the problem, only about 17% of people who would benefit from a hearing aid actually use one. The reasons include cost, stigma, limited access to audiological services, and — in many regions — a simple lack of trained professionals.

A 2019 review published in PMC estimated that hearing loss was the fourth leading cause of disability globally in the 2015 Global Burden of Disease study and the third leading cause of years lived with disability in the 2019 edition.

Where Smartphones Come In

The global penetration of smartphones has created a new category of hearing healthcare: app-based sound amplification and hearing testing. These tools do not replace clinical care, but they can meaningfully extend access — particularly for people in underserved areas, those who cannot afford traditional hearing aids, or those looking for an interim solution.

A 2022 pilot study published in the Journal of International Advanced Otology evaluated three smartphone hearing aid apps — including Petralex — against a calibrated clinical hearing aid and unaided conditions in patients with mild hearing loss. The study found that Petralex produced a 6% improvement in word recognition score, and was among the apps that showed measurable amplification benefit. (Koo et al., J Int Adv Otol, 2022)

Separately, research into smartphone-based audiometry has shown that calibrated app-based hearing tests can achieve thresholds within clinically acceptable ranges (±10 dB HL) compared to gold-standard audiometry in a soundproof room, making them a practical first-line screening tool.

What a Hearing Aid App Actually Does

A smartphone hearing aid app works by capturing ambient sound through the phone’s microphone, processing it in real time, and outputting amplified audio through the user’s earphones. The key difference between a simple volume booster and a hearing aid app lies in the signal processing pipeline.

Clinical hearing aids apply nonlinear amplification — quiet sounds are amplified more than loud ones, preventing discomfort while improving speech intelligibility. They also suppress background noise and manage acoustic feedback (the whistling effect). Petralex, developed by a research team at the Belarusian State University of Informatics and Radioelectronics, implements these same algorithms on consumer smartphone hardware in real time.

The team published their technical approach in peer-reviewed proceedings, including a 2017 IEEE ICASSP paper on real-time hearing aid implementation combining noise reduction and acoustic feedback suppression on smartphones.

The app uses an in-built hearing test to generate a personal audiogram, then automatically configures gain parameters across frequency bands to match the user’s individual hearing profile. Users can create multiple profiles for different environments — a quiet home, a noisy restaurant, a TV room.

Limitations and Honest Caveats

Smartphone-based hearing tools are not a substitute for a clinical hearing aid prescribed by an audiologist. Reviews of consumer apps consistently note that calibration is a significant challenge — results vary depending on the smartphone model and the earphones used.

The Petralex app explicitly states it is not a certified medical device and cannot be used with a doctor’s prescription. Its audiometric test is designed for app calibration, not clinical diagnosis.

In the United States, a 2022 FDA ruling created a new over-the-counter (OTC) hearing aid category, allowing adults with mild-to-moderate hearing loss to purchase hearing aids directly — without a prescription or audiologist visit. Petralex, however, is not an OTC hearing aid. It is a Personal Sound Amplification Product (PSAP): a category designed to amplify environmental sounds for people in specific listening situations, not to compensate for hearing impairment. PSAPs are not regulated as medical devices under FDA rules.

That said, for the estimated 400+ million people who cannot access or afford conventional hearing care, an accessible, inexpensive, science-backed amplification tool represents a meaningful step — not a final solution, but a practical one.