Navigating the World with APD: The Science of "Hidden" Hearing Loss

Have you ever found yourself in a crowded room, able to hear the "noise" of conversation but unable to make out the actual words? You might even have had a standard hearing test only to be told your hearing is perfect. If this sounds familiar, you aren’t alone. You may be experiencing Auditory Processing Disorder (APD).

At eargym, we are committed to bridging the gap between hearing science and real-world experience. Here is a deeper look at the research driving our understanding of APD and how we are working to support the community in 2026.

What is APD?

Auditory Processing Disorder is characterised by a poor perception of both speech and non-speech sounds. Unlike traditional hearing loss, which occurs in the ear, APD is often described as a brain-based hearing issue. Individuals typically report listening difficulties and behaviours consistent with hearing loss (HL), despite having a normal pure tone audiogram.

Why "Normal" Hearing Isn't the Whole Story

Current industry trends are shifting toward Ecological Validity, ensuring that the tests used actually match real-world auditory functioning. This concept refers to how well auditory tests and tasks match a person's actual auditory functioning in the real world. Rather than just testing in a quiet booth, researchers are now focusing on:

• Acoustic Realism: Understanding how we process sound in space (1).

• Adaptive Behaviour: How we purposefully adjust our behaviour to hear better in complex environments (2).

• Immersive Testing: To better reflect the real world, researchers like Sladen et al. (2024) are also utilising Virtual Reality (VR) to create realistic acoustic environments for more accurate assessment (3).

Auditory Biomarkers and the ADHD Connection

Many people assume that someone with ADHD struggles to follow a conversation simply because they are distracted. However, a landmark study by Lanzetta-Valdo et al. (2017) (4) suggests there is more to the story: the ADHD brain often struggles to physically process the sounds it hears.

What the study found:

Before receiving treatment, children with ADHD showed significant "hidden" hearing difficulties in two main areas:

• When different information was played into each ear at the same time, the brain’s "switchboard" became overwhelmed, leading to a high number of errors.

• Children struggled to keep sounds in the correct order (like identifying a sequence of high and low tones). If your brain can't keep sounds in order, following a fast-moving conversation feels almost impossible.

A Complete Reversal

The most exciting part of this research was the impact of treatment. The study followed these children for six months while they used standard ADHD medication (methylphenidate).

• Gradual Improvement: At the 3-month mark, their ability to filter out background noise and organise sounds began to improve.

• Success at 6 Months: By the end of 6 months, their hearing processing scores had improved so much that they were virtually identical to children without ADHD.

This research shows that many ADHD-related listening struggles are actually "processing" issues that can be identified and significantly improved. 

At eargym, we are using these insights to plan a 2026 trial with the NHS to help adults with ADHD strengthen these exact skills through targeted auditory training.

Why Hearing Health is Brain Health

When we think of hearing, we usually think of our ears. But scientists are now focusing on the "cognitive ear", the powerful partnership between your ears and your brain. Your brain does the heavy lifting of sorting, filtering, and making sense of every sound you hear.

Why This Matters for All Ages

Research has shown that when the brain has to work too hard to decode messy or "hidden" sounds, it uses up energy that it usually spends on memory and thinking.

• For Children and Adults: Identifying APD early is a superpower. It allows us to provide the right support, like auditory training, to make listening feel effortless rather than exhausting.

• For Long-term Health: A major study by Sardone et al. (2019) (5) found that looking after our "processing" health is one of the best ways to protect our brains as we age.

• The "Use It or Lose It" Principle: Just like physical exercise keeps your heart healthy, "hearing exercise" keeps the parts of your brain responsible for language and memory strong and active.

Bridging the Gap

While research (such as the Framingham study) shows a strong link between processing difficulties and long-term brain health, the message is actually one of hope and control. By identifying these "hidden" hearing issues early through tools like eargym’s Speech-in-Noise check, we can take proactive steps to keep our "cognitive ears" in peak condition for a lifetime.

Solving the Calibration Challenge

One of the biggest hurdles in remote audiology is ensuring that a test result is accurate regardless of whether you are using high-end headphones or basic earbuds. While some companies solve this by restricting tests to their own hardware, eargym is working to take a more inclusive approach.

• Biological calibration: We are working to implement "biological calibration" based on research by Masalaski et al. (2018).

• How it works: This method uses the hearing of individuals with normal thresholds to set a "biological" reference for specific device and headphone combinations.

• Proven reliability: Research has shown this mobile method is highly reliable, with only minor 1-2 dB deviations from professional clinical tests.

Training the "Cognitive Ear"

At eargym, we utilise the Digit Triplet Test (DTT) because it is a relative measure (SNR) where the ratio of speech to noise is what matters, not just the absolute volume, making it much more reliable for mobile devices.

But we don't just stop at testing. Our training programs are designed to strengthen the cognitive processes, like working memory and selective attention, that underlie our ability to understand speech in noisy, real-world conditions.

By combining cutting-edge SiN assessments with these validated calibration methods, eargym is building a foundation for a future where everyone has access to professional-grade hearing care and the tools to improve their quality of life.

Our goal is to prove that regular auditory checks and training can not only improve hearing but potentially help reduce cognitive decline. We are building the tools to help you hear and process the world more clearly.

Partner With Us

Are you interested in a research partnership to help shape the future of auditory health? We are actively looking to collaborate. Contact us here to discuss how we can work together.

References

(1) Goverts ST, Best V, Bouwmeester J, Smits C, Colburn HS. Acoustic Realism of Clinical Speech-in-Noise Testing: Parameter Ranges of Speech-Likeness, Interaural Coherence, and Interaural Differences. Trends Hear. 2025 Jan-Dec;29:23312165251336625. doi: 10.1177/23312165251336625. Epub 2025 May 6. PMID: 40329585; PMCID: PMC12059433.

(2) Beechey T, Naylor G. How Purposeful Adaptive Responses to Adverse Conditions Facilitate Successful Auditory Functioning: A Conceptual Model. Trends Hear. 2025 Jan-Dec;29:23312165251317010. doi: 10.1177/23312165251317010. Epub 2025 Mar 16. PMID: 40091404; PMCID: PMC11912170.

(3) Sladen DP, Diedesch AC, Zeitler DM. Localization and Speech-in-Noise Performance in a Virtual Reality Test Environment: A Pilot Study of Adults With Single-Sided Deafness Using a Cochlear Implant. Am J Audiol. 2024 Sep 3;33(3):981-990. doi: 10.1044/2024_AJA-23-00214. Epub 2024 Aug 22. PMID: 39173094.

(4) Lanzetta-Valdo BP, Oliveira GA, Ferreira JT, Palacios EM. Auditory Processing Assessment in Children with Attention Deficit Hyperactivity Disorder: An Open Study Examining Methylphenidate Effects. Int Arch Otorhinolaryngol. 2017 Jan;21(1):72-78. doi: 10.1055/s-0036-1572526. Epub 2016 Mar 31. PMID: 28050211; PMCID: PMC5205523.

(5) Sardone, R., Battista, P., Panza, F., Lozupone, M., Griseta, C., Castellana, F., Capozzo, R., Ruccia, M., Resta, E., Seripa, D., Logroscino, G., & Quaranta, N. (2019). The age-related central auditory processing disorder: Silent impairment of the cognitive ear. Frontiers in Neuroscience, 13, 619. https://doi.org/10.3389/fnins.2019.00619