How do we hear sound?
The perception of sound in humans occurs in the auditory center near the surface of the brain and is accomplished when electrical impulses are transmitted from the inner ear through the auditory nerve to a point in the brain under the auditory cortex. The auditory nerve has about 30,000 different fibers, and the type of electrical activity that occurs in these fibers matches the type of hearing and auditory memory. The cochlea, which converts sound waves into electrical impulses, is a noisy place, and the constant mechanical and electrical activity occurring on the 17,000 hair cells in the cochlea can now be monitored with sensitive computer-controlled audiometric devices.
Most of the sounds that people hear are continuous sounds, like speech and music.
During early childhood, new auditory experiences are stored in the almost blank, eagerly information-hungry auditory cortex. Later sounds received through the ear are constantly matched to familiar types of auditory memory. Each time an external sound is matched to a memory in the auditory cortex, we have the experience of hearing the sound. Putting these matching types together begins a process of evaluation. Another part of the brain tissue near the auditory cortex is involved in analyzing the meaning represented by the sound and interpreting the language. If we hear an unfamiliar language, we can hear the sounds but do not know what they represent.
What sounds mean
Sounds are extremely important for understanding the environment around us. Animals must have a very acute and specific sense of hearing because of the constant threat to their lives from predators. An animal’s acute hearing allows them to detect very small sounds from predators at great distances, which helps the survival of the population. These danger signals cause intense tension and trigger appropriate avoidance actions to avoid the attack, also known as the escape reflex. Our response mechanism is the same when we hear a car horn, and we subconsciously return to the sidewalk. Some sounds are perceived as warning signals, while others elicit a feeling of safety and pleasure. Every day we experience sounds that make us nervous, or sounds that are relaxing like nature or music.
Conditioned reflexes
When a sound has a special meaning, such as the sound of a baby waking up in the night, the creaking of a bilge, or hearing our own name, we automatically respond to it. This happens after a brief learning process, but these parties should remain at the same intensity throughout our lives. During sleep, the conscious part of the brain is inhibited, so we cannot hear, see or feel things. But even if a mother can sleep well during a stormy night, she will wake up immediately when the baby tosses and turns.
This means that faint sounds of significance can be filtered by the auditory pathway between the ear and the auditory cortex and be detected.
This conditioned reflex also triggers activity in the limbic system, which is associated with emotion and learning. It also activates the autonomic nervous system and finally triggers somatic defense or escape activities. The functions of the autonomic nervous system include muscle tension, increased heart rate and respiratory rate, sweat secretion, and in general the exact opposite of relaxation. This activity prevents sleep and prevents attention from being focused on unimportant things. Our daily activities consist of a sequential series of conditioned reflexes. Other examples of conditioned reflexes include the famous Pavlov dog test. Thus we label the sounds we hear and make explicit their meaning each day with an affective label that changes with our surroundings and each time we feel it. For example, the sound of a neighbor’s television set may be acceptable or unpleasant and annoying, depending on whether the neighbor is a friend we like or someone we hate for some reason.
The meaning of tinnitus sounds
In 1953, Heller and Bergman performed a simple classical experiment. They placed 80 people with normal hearing and no tinnitus in a completely soundproof room for 5 minutes and then asked them if they heard a sound. This test group thought they might want to have their hearing checked, but they actually experienced 5 minutes of complete silence. 93% reported hearing the same buzzing, pulsing and whistling sounds in their ears or heads that people with tinnitus hear. This simple test enabled almost everyone to perceive the electrical activity underlying each nerve cell in the auditory pathway as sound. Although some parts of the auditory system will be more active than others, each neuron will play a role in the final perception of tinnitus to some degree. It is appropriate to imagine the sounds heard in the Heller and Bergman test as music to the brain.
For those who do experience tinnitus, epidemiological studies show that 85% of people find tinnitus to be unpleasant and tension-inducing (something some tinnitus sufferers find unbelievable). If the loudness of the tinnitus were different, the interpretation of these sensations would be a different story. In fact we find that tinnitus is a very similar sound for people who are bothered by it and those who are not. The main difference is that those who find tinnitus bothersome consider it to be a threat, or at least an annoyance, rather than treating it as irrelevant.
Just as animals survive by focusing their attention on the sounds made by predators to alert them to danger, those who see tinnitus as a danger signal can only listen to it. This response is part of the human self-protection mechanism, even if it does not provide benefit in this case. Many patients complain that they lose the quiet they used to cherish before the tinnitus becomes persistent.
Persistent tinnitus is based on a conditioned reflex
The sound of tinnitus is caused by the electrical activity underlying the auditory nerve cells. A conditioned reflex is established for the sound of tinnitus, even in the case of tinnitus that causes mild annoyance. Since this conditioned reflex occurs in the subconscious area of the brain, what is thought about tinnitus at any given time is not related to the resulting response. It is the response to tinnitus that plays an important role in generating anxiety. That is, the degree of anxiety produced by the limbic system and the somatic tension response produced by the autonomic nervous system each time a tinnitus signal is detected. This mechanism is reflected by the diagram of the jastreboff model.
Tinnitus as a new experience
When tinnitus is first experienced as a new signal, there is no memory or classification of it. Any new experience will produce a feeling of discomfort due to the loss of the status quo and a change in the previously established homeostasis (a change in dynamic equilibrium). Until the meaning of tinnitus is properly evaluated, it is understandable that people will second-guess it. Due to this mechanism many patients experience only mild annoyance, but it may also be enough to cause a help-seeking action.
Tinnitus as a threat
For many patients, tinnitus can be quite threatening. Some people fear that tinnitus means they are suffering from some serious illness. Others believe that tinnitus implies ongoing damage to the inner ear, rather than a temporary, protective “shutdown”. Some patients fear that tinnitus is a precursor to a brain tumor, blood clot, or some serious brain disease. These anxieties are almost unfounded. Many people fear that tinnitus will become louder and louder and last forever without a cure. Even the notion that tinnitus violates their right to silence poses a threat, similar to the reaction of animals when their territory is violated. People are often afraid that continued tinnitus will disrupt peace and quiet, affect concentration at work, disrupt creativity and interfere with sleep.
Unfortunately these anxieties can be heightened by the advice of professionals and by other people’s accounts of their own experiences of tinnitus fear. There are still many doctors and professionals who tell patients that tinnitus is untreatable and will always be there. Other people’s fear of tinnitus means that their hearing is being damaged. Tinnitus may be the result of minor hearing damage rather than the cause, but the incidence of tinnitus and then hearing damage is still twice as high as in people with normal hearing. In both cases the threat of tinnitus is exaggerated.
Finally many people with tinnitus are angry about the treatment, or lack of treatment, for tinnitus and the inappropriate advice they receive. They may regret the treatment they received for what they thought was the cause of their tinnitus. Fear, anger, and regret are powerful emotions that can reinforce survival-related conditioning and therefore greatly increase attention to tinnitus. Our experience is that tinnitus improves when the patient overcomes these emotions and stops envisioning damage.
Tinnitus in a state of morbid fear
In some patients the extreme fear of tinnitus leads to a pathological fear, similar to the pathological fear of spiders, frogs, small animals, flying insects. The fact that many patients have these fears indicates that common mechanisms are at work. A slow desensitization process is applied when retraining morbid fears, allowing the patient to face what is feared, first learn to tolerate it, and then accept it as not threatening in any way. Many aspects of tinnitus retraining are similar to these techniques.
Many people have a negative perception of tinnitus even though their reaction is mild. But even if strong emotions are not triggered, the worry and discomfort remain, and the limbic and autonomic systems are still activated, producing a disturbed emotional response that reduces quality of life. These help-seeking properties of tinnitus arise outside of the auditory mechanism and therefore cannot be treated by hearing and ear-related methods alone.
Tinnitus Retraining Treatment
Successful treatment of tinnitus in the clinic is the result of retraining and relearning. No matter how loud and unpleasant tinnitus once was, it begins to subside when it loses its bad meaning, and many patients will not hear it for a long time. In most cases, however, the patient’s stubborn perceptions are difficult to change.
Retraining the subconscious auditory system to accept tinnitus as a naturally occurring condition does not represent a lifetime of suffering, nor is it a warning sign. This process can last for months or even years. A multidisciplinary team for the retraining of tinnitus should be guided by multiple experts experienced in this field. For those patients with co-existing or pre-existing anxiety or depression, it may take longer to change their perception of their tinnitus.
Retraining is not just an abstract learning process. After sound is transmitted from the inner ear and before the brain becomes aware of it, there exists a subconscious area associated with hearing, a part of the nerve cell that picks up signals on the basis of auditory need.
Think of how we can hear our own name, the sound of a car horn in the distance, the sound of a baby tossing and turning in its sleep, but not the sound of rain pounding on the roof or waves lapping against the shore. Retraining involves rearranging and reprogramming the network system of selective sound acquisition in the auditory system. Because although tinnitus is a naturally occurring sound, they are considered to be a threat to life or quality of life. Tinnitus retraining first includes recognizing the cause of the tinnitus. It begins with a proper examination by an ear specialist, followed by an explanation of what is happening in the ear and brain that is causing the tinnitus. However, specialists who believe that tinnitus is a phenomenon that occurs in the ear are not helpful. We are now faced with great difficulties due to the fact that the traditional approach to the treatment of tinnitus based on damage to the inner ear rather than on the neurophysiological model still prevails.
It is important to recognize that what are considered annoying and seemingly endless tinnitus sounds that affect the quality of life are actually weak electrical signals in the auditory conduction pathways that are consistently present everywhere. By providing appropriate counseling, specialists can change the perception of tinnitus as a dangerous or unpleasant experience, which is considered unchangeable.
Adaptation of perceptions and responses
The persistence of a stimulus often leads to a process of adaptation, and as long as this signal has little aspect of meaning, the response to the stimulus becomes less and less. The final stage of this process is that the signal is no longer detected and the nerve cells of the cortex no longer respond to it. For tinnitus this means that one can no longer hear it, even when deliberately listening to it. This result can be achieved during training. This process usually takes up to 2 years, but during the initial stages of training tinnitus slowly becomes less annoying (even though it is still perceived as a loud sound). This process is called the adaptation response. Over time, the tinnitus becomes less and less annoying and eventually disappears or becomes a background noise in a quiet environment (perceptual adaptation). But this does not happen when the tinnitus is still perceived as a red flag or a bad experience that needs to be continued.
Hearing loss and tinnitus
When there is a hearing loss, the ear itself does cause tinnitus. The hearing loss may be mild, or simply a high-tone hearing loss. Any tendency to make an effort to hear will exaggerate the tinnitus signal in subconscious areas of the brain, making the tinnitus signal more readily available. This is where the importance of wearing hearing aids to correct severe hearing loss as part of the tinnitus treatment comes into play. However, in clinical practice we often find that hearing aids configured for people who are not aware of tinnitus treatment may aggravate tinnitus. In some cases, changes in inner ear function may play an important role in causing tinnitus, such as Meniere’s disease and auditory neuroma, but retraining methods are not related to the triggers of tinnitus.
In determining the persistence of tinnitus and our emotional response to it, it is important to distinguish between the role of the ear in the emergence of tinnitus and the central processing role of the brain outside the auditory system. Despite the importance of hearing loss in the development of tinnitus, recent studies of tinnitus patients have shown that there is no statistical difference in hearing between the tinnitus group and the normal population.
Wearable Sound Generators (WSGs)
Wearable sound generators (WSGs) are functionally different from mufflers in that they are identical in appearance. It was once thought that tinnitus maskers could make the sound of tinnitus inaudible. Now it has been shown that tinnitus maskers do just the opposite, because tinnitus can only be heard during adaptation. When one cannot feel a signal one cannot adapt to it. Imagine if you could adapt to it by simply avoiding the spider you hate. Better results can be achieved by applying broadband noise with low loudness that can be heard simultaneously with tinnitus. Broadband noise includes all the frequencies that activate all the nerve cells in the subconscious neural network, making them more easily rearranged so that tinnitus is no longer found. It also reduces the contrast between tinnitus and complete silence. Thus it can temporarily reduce the tension caused by tinnitus in its own way, but the tinnitus masker will not achieve long-term adaptation if it is not complemented by TRT-education-de-mystification-reevaluation-desensitization.
Avoiding silence
The onset of tinnitus is often associated with silence. Most tinnitus is heard at night in a well-soundproofed bedroom or in a quiet living room. The persistence of tinnitus depends not only on the meaning added to the tinnitus, but also on the contrast it produces with the surroundings. Contrast greatly increases the intensity of any sensation. A tiny candle in the corner of a large dark room can look dazzling, and when the translucent light is turned on, the candle is almost invisible for this reason. Tinnitus sufferers should avoid complete silence and retrain to use a hundred noises regularly to reduce this contrast. For all intents and purposes, a variety of sounds should be applied. Make sure that pleasant background sounds are always present (a large slowly rotating fan, an open window, or buy an instrument that makes natural sounds). Choosing one that works for you will take some time. Avoid masking tinnitus, but is some other sound is present day and night. Many tinnitus sufferers have auditory allergies, so they often seek out very quiet environments. In this respect, they are their own worst enemy. In all cases, the silence is broken by applying a variety of unpleasant sounds. Although the application of broadband noise itself can temporarily relieve the discomfort caused by tinnitus, it is difficult to achieve long-term results if it is not combined with retraining. De-mystifying the mechanism of tinnitus is a crucial part of this therapy for patients to understand.
While the perception of tinnitus as a threatening signal persists, the survival conditioning mechanism of tinnitus in the subconscious area of the brain is continuously monitored in the subconscious area. Retraining therapy is currently available at only a few centers, but more and more otologists and audiologists are learning and applying this technique.