The Silent Trace of Noise:
An Interview with Sema Satıcı

I completed my undergraduate education at İstanbul University in 2017. That same year I began my master’s at Marmara University and finished it in 2019. In the meantime, in 2018, I started working as an audiologist at Kanuni Sultan Süleyman Training and Research Hospital in Küçükçekmece, İstanbul. In 2020, the Ministry of Health assigned me to the then newly opened Başakşehir Çam and Sakura City Hospital to support setting up the clinic. After continuing there for about a year and getting the clinic into a certain routine, I began working as a lecturer in the Department of Audiology at the Hamidiye Faculty of Health Sciences, University of Health Sciences, where I still work. In 2021 I decided to continue with a doctorate at Marmara, and I graduated from the doctoral program last year.

When I put it this way, it sounds like quite a long journey. Actually, the one thing I’ve been sure of about myself since my undergraduate years was that I would either continue as a clinical audiologist or pursue an academic career; I couldn’t really picture myself in any other field. After experiencing both, academia started to appeal to me more and I leaned that way — but I still love the clinic and seeing patients, and I still do.

I think I graduated from Cerrahpaşa already well-equipped. Afterwards, having continued my graduate education at Marmara University — which has a deep-rooted structure in audiology — has played a big part in developing my identity as a researcher and shaping my clinical perspective. Working for 3.5 years in hospitals with very high patient flow, while also seeing patients during our clinic days at Marmara, allowed me to develop rapidly on the clinical side.

This process taught me that in the clinic every patient is different from another; that assessments must rest not only on test results but on a detailed history and a holistic perspective. Academic work, on the other hand, showed me how the questions we encounter in the clinic can be answered with scientific methods. That’s why today I try to keep an evidence-based approach at the center of both my clinical practice and my research.

Today noise has become an unavoidable environmental exposure, especially for people living in big cities. Because of traffic, public transport, construction, crowded social settings and the habit of listening to loud music, many people are exposed to high sound levels throughout the day without realizing it. Noise is essentially an environmental pollutant — just like air, water or soil pollution. But because its effects are not as visible as theirs, society doesn’t really think about it much. With the recent rise in recreational noise as well, we see that the World Health Organization has intensive efforts to inform and raise public awareness on the subject; public-information efforts in this direction are increasing in our country too.

Absolutely. Of course, the most concrete effect of noise is on the auditory system; but beyond that, we know from studies that it has many effects, both physiological and psychological. Constant exposure to noise can raise stress levels, impair sleep quality, negatively affect attention and concentration, and cause a marked decline in overall quality of life. Especially in metropolitan life, these effects accumulate over time and can lead to significant consequences, both physically and psychologically.

Observational and experimental studies show that exposure to noise causes annoyance, affects the endocrine system, increases the incidence of diabetes, disrupts sleep and causes daytime sleepiness, raises the risk of hypertension and cardiovascular disease, can trigger psychological problems such as anxiety and depression, and impairs cognitive performance.

In that study, in individuals occupationally exposed to city-traffic noise for long periods, we assessed not only hearing thresholds but also factors that directly affect quality of life, such as noise sensitivity and hyperacusis. Such studies show that noise is not just a matter of hearing loss but a multidimensional public-health problem affecting an individual’s daily life and communication skills.

For this reason, today the most important approach is to strengthen preventive audiology practices rather than to treat hearing loss once it has occurred. Instilling safe-listening habits, reducing exposure to loud sound, and having at-risk individuals undergo regular hearing evaluations are of great importance in protecting hearing health.

For many years, noise was thought to cause only permanent hearing loss. But studies in recent years show that even when standard hearing tests are normal, noise can cause damage to the auditory nerve connections; and that this can manifest, especially in noisy environments, with complaints such as difficulty understanding speech, increased listening effort and auditory fatigue. In other words, the fact that the audiogram is normal alone may not mean that the auditory system is completely healthy.

Hidden hearing loss is defined as the impairment of auditory neural processing and auditory acuity in people with normal audiometric thresholds — especially in noisy environments. It has many different mechanisms; but the most widely accepted and best-documented one in the literature, sometimes used synonymously, is “cochlear synaptopathy”. We can define this as the degeneration of the cochlear ribbon synapses without loss of hair cells or spiral ganglion neurons. The reason it is “hidden” actually lies within this mechanism.

Recent studies have shed light on the vulnerability of cochlear nerve synapses and their peripheral synaptic connections, especially in cases of noise exposure and aging; they showed that these are often at greater risk than the hair cells themselves. In some cases, these synapses can even be destroyed before the hair cells are damaged. This leads to a situation where damage to the synapses between the inner hair cells and the cochlear nerve fibers can have very little effect on behavioral hearing thresholds until significant nerve loss occurs.

Moreover, after noise, synaptic loss mainly affects nerve fibers with a low spontaneous firing rate and high thresholds. Damage to these fibers leads to reduced responses to suprathreshold sounds and impaired auditory sensitivity in complex acoustic environments. In contrast, the surviving high-spontaneous-rate fibers preserve threshold sensitivity and frequency tuning and facilitate the recovery of normal hearing thresholds — so on a standard test the picture can look ‘normal’.

In my thesis, I divided 50 participants aged 18–30 with normal hearing into two groups — high-risk (HR) and low-risk (LR) — according to their annual headphone-exposure levels recorded via smartphone apps. Participants underwent high-frequency audiometry, ABR, the Turkish Matrix Sentence Test, a behavioral listening-effort measurement and the P300 test; listening effort and P300 were measured under varying signal-to-noise ratios (SNR). For cognitive skills, I assessed working memory with the reading-span test, attention with the Stroop test, and short-term memory with the visual-auditory digit-sequence test.

The ABR and Turkish Matrix Sentence Test findings showed signs of noise-induced cochlear synaptopathy in the HR group. In this group, as the SNR decreased, there was a statistically significant increase in listening effort. Also, in the HR group there was a significant decrease in P300 amplitude in response to SNR changes; in the LR group, there was no significant difference. In the cognitive tests, however, there was no statistically significant difference between the two groups.

Actually, even though we saw no difference in the cognitive tests, the differences we obtained in the listening-effort measurement and in P300 allowed us to see the effect of loud music both on the auditory system and on all the cognitive processes needed to understand speech. Although no clear decline has yet been observed in general cognitive functions — attention and memory, for example — the increased consumption of cognitive resources associated with auditory cognition offers an important clue that there may be long-term effects. For this reason, I think more longitudinal studies are needed in this area.

‘I can hear but I can’t understand’ is a very general complaint. In audiology, before attributing it directly to hidden hearing loss, all possible pathologies must be ruled out. Although hidden hearing loss can be effectively studied in animal models with a combination of invasive physiological and histological tests, this is not possible in humans. Therefore, here it’s necessary to use many tests together rather than a single one. Even so, making a diagnosis is still very difficult, because there is no specific norm or diagnostic criterion — there is no criterion like ‘if the wave I amplitude on ABR is below such-and-such a value, hidden hearing loss can be suspected’.

At this very point, I think that, as in many areas of audiology, history-taking is critically important. If a person persistently voices a strong complaint of hearing loss but their tests come back normal; if they say their attention is easily distracted and they can’t focus in noisy environments; if there is a complaint of tinnitus or hyperacusis, suspicions of hidden hearing loss begin to form in my mind. I also always ask about the patient’s occupation — we encounter it very often in teachers, for example — their noise exposure, and especially in the young group, the duration and level of headphone use.

Afterwards, I always apply high-frequency audiometry and speech-in-noise tests. If possible, electrophysiological measurements — ECochG and ABR — can be added. But as I said at the outset, it’s hard to say ‘hidden hearing loss’ directly; it will be much more accurate to proceed by combining the findings with other test results.

As you noted, the habit of listening to loud music is very common, especially among young people. In its latest report, the WHO states that ‘worldwide, 1.1 billion young people may be at risk of hearing loss as a result of unsafe listening practices’ — a rather serious figure when you look at it. At this point, I think safe listening should become a way of life. In its simplest form, we can talk about the ‘60/60 rule’: if we take care, when using headphones, not to exceed 60% of the volume and to listen for at most 60 minutes a day, we won’t exceed the safe-listening limit.

Beyond that, in recent years smartphones and smartwatches can track noise levels or your headphone-listening levels; if possible, I think these apps are quite useful too. Devices sometimes give warnings like ‘the sound is too loud, turn it down’; these should be heeded. And sometimes, especially on public transport, using noise-cancelling headphones instead of turning up the music to drown out external sound can be a good method of personal protection.

Yes. For individuals working in noisy environments, a protocol defined in the regulations must already be followed; they must use the ear protectors provided by the employer. But sometimes people don’t use them — and here I think that, as audiologists, we need to provide counseling and instill awareness of protection from noise. Because using ear protectors only at the workplace is sometimes not enough; people also need to know how to protect themselves from noise in their daily lives. Especially if hearing loss has already begun, these kinds of information become far more critical for the person.