Tinnitus patients who pay attention will find a common phenomenon, that is, in a noisy environment, the tinnitus will feel less loud or even disappear completely, while in the dead of night the tinnitus will seem very obvious and distracting.
This is because the noisy environment plays a role in masking tinnitus. When it comes to the masking of tinnitus, it is generally believed that external sounds are used to mask tinnitus, but in fact this is only a very old empirical statement. For a long time in the past, it was only about using the masking phenomenon, which is fundamentally different from the tinnitus masking therapy we are going to elaborate here. This is because as the understanding of tinnitus has deepened and the technology of producing masked sounds has improved, tinnitus masking has changed from the accidental and temporary masking phenomenon (i.e., temporary masking).
This is because with the increased understanding of tinnitus and improved techniques for producing masked sounds, tinnitus masking has evolved from the previous results of incidental and temporary masking (i.e., temporary relief) to a more targeted and systematic treatment for long-term relief or even complete suppression of tinnitus, known as tinnitus masking therapy. Now if one were to define tinnitus masking therapy, it would be described as follows.
A method in which a specific external sound matching the loudness of the tinnitus tone is selected as a masking sound after a series of tests on the nature of the tinnitus, and the masking sound is listened to under medical supervision to suppress the tinnitus or relieve the tinnitus symptoms.
The method. The lack of instruments to test the nature of tinnitus and the technical means to produce tinnitus masking sounds has greatly hindered further research into tinnitus masking treatment and has made it difficult to develop an effective treatment method. Today, it is possible to test the nature of tinnitus and to obtain a variety of different sounds to match it, and to reproduce them in the laboratory for use by patients. This has allowed us to develop masking treatments for tinnitus. The mechanism of action, influencing factors, treatment options, recommended treatment modalities, common errors, and examples of application of tinnitus masking therapy are described below.
It is important to note that it has been argued that tinnitus masking does not require the same or similar pitch, but that white noise can serve to mask tinnitus. This is true even for the first half of the book. However, the author’s view, like that of most scholars, remains that the masking sound should be of the same or similar pitch to tinnitus. Obviously, this is a controversial issue that requires further research.
I. The mechanism of masking therapy
Since masking therapy uses a sound to mask the sound of tinnitus, some doctors and patients ask whether it is a kind of physical therapy (physiotherapy), or a kind of “fighting poison with poison” (a sound to restrain another sound). The answer, of course, is no. Such an understanding distorts the essence and connotation of tinnitus masking therapy.
First, let’s understand the physiological mechanism of sound masking. Experimental evidence for the site of the sound masking phenomenon has been found in the cochlea, the auditory nerve and all levels of the auditory centers. For example, the basilar membrane of the cochlea is the first anatomical site where masking begins, and the stronger masking sounds cause larger vibrations in the basilar membrane so that the smaller vibrations in the basilar membrane caused by the test sounds are not easily detected and acoustic masking occurs. In the auditory nervous system, masking noise can inhibit the evoked firing of some neurons at all levels of the center, as well as increase the threshold and decrease the amplitude of the auditory nerve, brainstem, and cortical evoked potentials. These facts may provide an explanation for the masking phenomenon of hearing to some extent.
Secondly, we can elaborate on the physiological mechanisms by which tinnitus arises. It is well known that tinnitus can be either a clinical symptom manifested by the dysfunction of a certain part of the whole auditory system or it can be due to mental or psychological factors. At least 80% of tinnitus originates from the periphery (i.e. cochlear tinnitus), and the main pathway of this ear disease caused by the inner ear may be a lesion that causes damage or degeneration and necrosis of hair cells or auditory nerve endings, resulting in dysfunction or central control disorder, which may cause the auditory nerve to send some pathological signals on its own, i.e. to produce an abnormal spontaneous discharge activity that is perceived (incorrectly encoded) as a sound.
Experiments have been performed to show that.
1, there is an extensive dependent connection between intracochlear cells (inner and outer hair cells, supporting cells, etc.), i.e., cellular communication.
2, The efferent nervous system has an inhibitory effect on the excitability of the inner and outer hair cells.
3, Noise can activate the efferent nervous system and inhibit the excitability of inner and outer hair cells.
4.Various neurotransmitters (such as 5-hydroxytryptamine, GABA, etc.) are involved in the formation of tinnitus.
5.Tinnitus is closely related to learning memory.
6.Tinnitus is related to central plasticity.
7. Tinnitus is a result of the cumulative effect of lesions.
8. The function of the efferent nervous system is regulated by the cerebral cortex (i.e., influenced by mental and psychological factors).
To facilitate the understanding of the mechanism of tinnitus masking treatment, let us imagine the formation of cochlear tinnitus. When the inner and outer hair cells are attacked for some reason, the cells undergo a process that includes a dying link, during which the adjacent cells exhibit a series of responses, such as increased cellular activity, due to intercellular communication. In addition, the activity of efferent neurons innervated by the brain decreases and the production of neurotransmitters is altered, resulting in abnormal spontaneous firing activity of afferent neurons and their transmission to the center. In this case, long-term persistent tinnitus may be observed. In this case, if the patient has certain psychological and psychiatric factors, a vicious cycle of tinnitus aggravation will be formed. The mechanism of masking is to select a narrow band of noise corresponding to the hair cells with enhanced activity in order to excite the efferent nerves innervating these cells, thereby reducing the spontaneous activity of the hair cells and restoring them to normal activity. After a period of stimulation training, the excitability of some or all of the efferent nerves can be restored, and the abnormal spontaneous discharge activity can be reduced or the spontaneous discharge activity can be restored to normal. The tinnitus can be relieved or even disappeared by erasing the central memory of the tinnitus and destroying its plasticity. Therefore, when implementing masking therapy, it is important to exclude unfavorable factors that affect the function of the efferent nervous system, such as mental tension and psychological factors. Therefore, it is recommended that masking therapy should be combined with relaxation therapy, which is the masking relaxation therapy we advocate, that is, when masking therapy is performed, the patient should be instructed how to achieve a more relaxed state to listen to the masked sound and combine it with certain relaxation exercises. This also determines the indications for masking therapy.
I. Tinnitus masking therapy program
1. Factors affecting the effect of tinnitus masking therapy and determination of masking parameters.
Wegek and Lane confirmed that the masking effect is partly dependent on the frequency of the masking tone. For tinnitus masking as well, the tinnitus masking sound needs to contain the frequency range corresponding to the tinnitus tone, therefore, matching the tinnitus tone is the most important part of tinnitus masking. Knowledge of the individual patient’s minimal masking curve can also assist in the appropriate selection of masking sounds and masking intensity for tinnitus relief. In conventional auditory physiological masking, it is difficult to mask a noise with a single pure tone, and conventional masking does not produce residual suppression, yet clinical investigations have found residual suppression effects in 89% of tinnitus patients, suggesting that tinnitus masking is mechanistically and formally distinct from conventional auditory physiological masking.
Although conventional masking can be obtained through efforts to obtain contralateral (central) masking, it is difficult to obtain it at low masking sound intensities. In tinnitus masking, on the other hand, contralateral masking is easily obtained in some cases, but certainly not in all cases. Whereas conventional masking results indicate a strong intensity dependence, tinnitus masking results indicate that it is not entirely intensity dependent, and in some cases the masking effect can be produced at a lower intensity than the tinnitus match, while in other cases the maximum intensity of the masker does not mask low intensity tinnitus. Snyder found that central masking increased with increasing frequency and also found that central masking increased with decreasing masking noise bandwidth, and we also found that contralateral masking could be used for some tinnitus patients.
Tinnitus masking therapy is influenced by certain parameters and factors, and it is important to understand these influencing factors for the selection of tinnitus masking therapy parameters to improve the efficacy.
(1) Accurate matching of tinnitus patient tones, acoustic nature of masking sound: To determine the nature of the patient’s tinnitus (e.g. tone, etc.), when multiple tones are used, the main tinnitus tone can be selected, and the effective masking sound signal frequency should contain the main tinnitus tone, i.e. the effective masking sound is a narrow band noise with the same central frequency as the main tinnitus tone.
(2) Masking sound stimulus intensity and masking time range: Since the hearing of tinnitus patients is mostly abnormal, especially the hearing loss in the frequency range near the tinnitus main tone, in order to make the masking sound stimulus play an ideal masking role, there must be
Therefore, in order for the masking acoustic stimulus to play an ideal masking role, there must be an appropriate loudness, but if it is too loud, it is difficult for the patient to accept it and may even cause further acoustic damage. In addition, under the condition of achieving a certain loudness, masking time, the course of treatment also has a great impact on the masking effect.
(3) Hearing loss of the patient: Hearing loss of the patient is also a factor that must be considered, because an accurate audiogram can guide the selection of tinnitus masking treatment parameters (such as masking sound intensity) and the selection of ipsilateral, contralateral or bilateral masking, etc.
2. Instruments for tinnitus masking
(1) Hearing aid: It is suitable for patients with mild to moderate deafness who have tinnitus with frequencies below 4kHz, because it only increases the external sound (noise, speech), and the electrical characteristics of hearing aids determine that the amplified sound frequency is mainly concentrated below 4kHz, therefore, the target and effect are limited. Of course, for patients with tinnitus accompanied by hearing loss, the preferred option for treating tinnitus is optional hearing aids, which can try to treat tinnitus while improving the patient’s degree of hearing impairment.
(2) Tinnitus masking hearing aid: It is a combination of hearing aid and tinnitus masking device, which are all imported in China and are expensive.
(3) Small masking devices: There are box-type and behind-the-ear masking devices from Tianjin Hearing Aid Factory, and behind-the-ear and in-the-ear masking devices from foreign companies. Because of their limited frequency range of masking sound, they are not targeted for individual tinnitus sound and cannot achieve the best effect.
(4) Specialized tinnitus masking instrument: an instrument that can produce broadband and narrowband noise with adjustable frequency range and noise output intensity. Here we suggest that hospitals with conditions can use pure tone audiometer as a special masking instrument for tinnitus masking treatment, and the effect is very good. Pure tone audiometers have the best treatment effect among similar masking treatments because of their good acoustic characteristics and strong narrow band frequency targeting. However, they are large, expensive, and inconvenient to carry, and patients must go to the hospital for treatment, so they are limited.
(5) “Walkman” or “CD” method: The best masking sound is recorded on tape or CD in the laboratory, and then played on the “Walkman” or CD player, and the volume is adjusted to control the intensity. to control the intensity.
However, the following points should be noted.
① The recorded tapes should be high fidelity;
② “Walkman” quality, mainly refers to the sound fidelity, especially the headphone frequency response characteristics cover the recorded sound frequency, if there is distortion, it affects the masking effect.
③Listen to the way of masking sound: moderate loudness, moderate use time. Therefore, patients should be carefully instructed that the volume should be controlled at the lowest intensity that can mask tinnitus when used, and the time should not be too long. The fidelity of “CD” is higher than that of “Walkman”, and it is an ideal form of tinnitus masking if it can be paired with broadband headphones.
III. Recommended masking treatment mode
Here I recommend several masking modes based on clinical application experience for reference only. As a matter of fact, the tinnitus of patients in clinical contact is complex, and if we summarize the effect of masking treatment on patients in practice, from a certain point of view, patients will teach us how to make a correct judgment and choose the appropriate masking mode for the endlessly changing tinnitus.
1.Hearing aid mode: Deaf patients with tinnitus main tone below 4kHz with mild or moderate hearing loss.
2.Pure tone audiometer mode: for patients with tinnitus of various tones.
Choose a narrow band noise with the same central frequency as the main tone of tinnitus, masking sound intensity of 10~20dB SL, ipsilateral air conduction to give sound, let the patient listen for 30~45 minutes, ensure 1 time/day, 2 times/day if possible, the course of treatment is at least 1 month, no interruption in the middle. For conductive, mixed and no hearing impairment or mild hearing impairment, the main tone below 3kHz can be given by bone conduction headphones (especially for bilateral tinnitus patients). Use Tianjin Hearing Aid Factory’s cassette or behind-the-ear masking device to assist treatment (used at home), 3 times/day (morning, noon and evening), 30~45 minutes each time, at moderate volume. For those who are effective in treatment, treatment should be continued to consolidate the effect.
3.”Walkman” mode: For patients whose tinnitus tone is below 4kHz, we record the narrow band noise matching the tinnitus tone output from the pure tone audiometer, 3 times/day (morning, noon and night), 40~60 minutes/time, with moderate volume. Of course those who are able to do so can first undergo a 1-month period of pure tone audiometer mode therapy in the hospital optimally. Observe the efficacy to 3 months as a course of treatment tracking.
4.”CD Disk” mode: Especially for patients whose tinnitus main tone is above 6kHz, you should choose headphones with good frequency response characteristics, otherwise it is difficult to achieve the best effect, otherwise it is the same as No.3. Because it is convenient and feasible, and can record high-fidelity masking sound, this mode is a masking therapy mode worth recommending and promoting.
IV. Precautions for tinnitus masking therapy
1. Bilateral asymmetric tinnitus
Bilateral tinnitus is very common in clinical practice, accounting for 67% of patients. Often tinnitus patients are only aware of tinnitus on one side, as it is only apparent on one side. It is easy to make the following mistake: clinically, the patient is given a masking sound in the same ear and then asked if he can hear the tinnitus, and the patient usually answers that he can still hear the tinnitus. In reality, however, the tinnitus is no longer audible on the masked side; instead, the patient responds that the tinnitus is coming from the other side. Therefore, it is important to ask the patient not only if the tinnitus is heard when masked, but also on which side it is heard.
It is often found clinically that patients with asymmetrical tinnitus are usually not aware of the lower intensity side. In this case, bilateral tinnitus can be confirmed by masking the tinnitus on the high intensity side into residual suppression and confirming the presence of tinnitus on the other side. In fact, the tinnitus is always present, but it is the residual suppression process that temporarily eliminates the dominant tinnitus and makes the tinnitus on the other side visible. Bilateral tinnitus is sometimes asymmetrical in tone, so that the nature of the tinnitus differs between the two ears in terms of the type of sound. Often the patient is aware of this but does not complain accordingly. When this occurs, it is important to decide, for example, whether
The two types of tinnitus are equally painful for the patient. If one side of the tinnitus is not important to the patient, then bilateral masking is not necessary, and it must be determined that the ignored tinnitus on that side can indeed be ignored. Some patients in the clinic may say “I have severe tinnitus on my right side and a little on the other side”. The side with severe tinnitus should be treated first. If the tinnitus on that side is relieved or greatly reduced during treatment, the other side may be brought to the attention of the patient.
2.High frequency hearing loss
The following situations are often encountered in clinical practice.
(1) The patient’s tinnitus is high pitched.
(2) The patient has a high frequency hearing loss in the tinnitus ear with a tinnitus tone matching frequency of 6 kHz. If broadband noise is used, the patient is found clinically in such cases to simply reject the low and middle frequency tones that are more unpleasant than the tinnitus due to the excessive low and middle frequency components. The solution to this problem is to select targeted narrowband noise, i.e., narrowband noise with a center frequency of 6 kHz (see Case 1 for details), but in this case masking sound selection should be considered acceptable to the patient, and the most effective or efficient masking sound for high-pitched tinnitus is often “sharp” or “high-pitched “.
3. Drift of tinnitus tone For many tinnitus patients a long period of tinnitus tone testing should be maintained, especially during the treatment period when the patient is concerned about the change in tinnitus tone
Two conditions can occur during the course of treatment.
(1) tinnitus tone drift.
(2) As a result of tinnitus primary tone treatment
In both cases, the tinnitus tone and the tinnitus masking curve should be retested, the masking treatment parameters should be readjusted and the change in tone should be closely monitored (see case 3).
4. Doctor-patient relationship
Tinnitus treatment is persistent and difficult work that requires close cooperation and joint efforts between the physician and the patient, and expects the patient to religiously comply with the regulations made by the physician regarding the treatment plan. When a patient suffers from tinnitus, especially if it has developed into a distressing and persistent tinnitus, many patients are left in a state of painful bewilderment. Therefore, first of all, after the patient excludes organic disorders, the doctor should patiently and briefly teach the patient about tinnitus, make a preliminary diagnosis based on the patient’s specific condition and examination results, and briefly explain the pathophysiological mechanism of tinnitus, its effects, and various factors that trigger and relieve tinnitus. Secondly, communicate with the patient about tinnitus (including during treatment), such as the main hazards of tinnitus to the patient and the patient’s understanding of tinnitus, to correct some unhealthy views of the patient and to create a sense of trust and authority in the doctor. Finally, the patient should be introduced to the relevance of masking therapy to his or her treatment, be prescribed treatment, and be instructed to carry out some rules carefully, so that the patient should follow the doctor’s arrangement religiously.
5. Contralateral masking
When masking is considered, there are two types of bilateral tinnitus patients: unilateral masking that produces both contralateral and ipsilateral masking effects, or ipsilateral masking only. In either case, treatment with masking is required to achieve relief from the tinnitus. Contralateral masking is often present in clinical practice and the possibility of contralateral masking should be tested and used when appropriate. In the case of tinnitus with a “dead ear” on one side, the effect of contralateral masking should be tested, and in such cases contralateral masking is necessary, especially if contralateral masking is successful.
6. Masking intensity
In order to obtain the maximum residual suppression during masking, it is usually a mistake to increase the masking intensity inappropriately. After the lowest intensity effective masking sound effect, will experience a short time residual suppression effect; these are only natural characteristics, however, patients or some doctors find residual suppression effect and want to appear the maximum residual suppression effect. Their reasoning is that if low intensity masking produces some residual suppression, then increasing the intensity of the masked sound should produce greater residual suppression. This is not the case, and studies have shown that large masking does not produce greater residual suppression. Therefore, if the masking intensity is increased excessively, patients often feel that the masking is too loud and become bored, or become uncomfortable and abandon treatment, which may lead to further hearing loss in severe cases.
Doctors and patients should have a good understanding of the residual suppression effect. The appearance of complete residual suppression is most like a cure, because then the tinnitus disappears completely. Therefore, it is important for tinnitus patients to understand how to take advantage of the residual suppression effect. When they understand that a partial residual suppression effect is developing, it indicates that masking therapy is having an effect and they should gain confidence and persistently continue treatment. In addition, because masking is just another sound, many physicians and patients do not want to try masking because, for the most part, they believe that they can no longer do anything for tinnitus relief and are desperate for tinnitus treatment. Masking alone does not work for all patients, so we believe that the goal of masking therapy is to produce tinnitus relief rather than to pursue residual suppression, and when residual suppression is present, it will respond as an indicator of a good indication for treatment. When the residual suppressive effect is absent or transient, it does not mean that masking therapy does not provide relief of the patient’s tinnitus. Usually, tinnitus relief is present and evident at the beginning of masking therapy, when many patients know that masking therapy will be successful. However, in some cases where tinnitus relief is not apparent at first, we advocate that the patient should not take the attitude of trying for a week or two or even once, but rather advise the patient to continue treatment with persistence and perseverance, and that persistence is the result.
7.Masking is just masking
Patients with tinnitus may tell us that they have used masking therapy before but failed, and thus refuse to accept masking therapy treatment. In this case, it is best to ask carefully about the masking method used (including the masking method, masking signal, parameters, etc.). Some patients may only use a simple noise-generating masking device. Although they are using masking sound masking, this masking is only a formal masking and does not achieve the real meaning of masking therapy.
8. Central fixation of tinnitus (location) A serious mistake more likely to be made
For those patients whose tinnitus is located in the center of the head, not the ear. When the patient is asked where he hears the tinnitus, the answer is often repeated that he does not know where he hears it. On the other hand, many answer “in both ears” and rarely say “in the head”, “at the back of the head”, or “at the top of the head “. For those who do not know where they hear tinnitus, it is often reflected at once that the location is often mostly “in the head”.
Considering that the patient’s tinnitus is located at the top of the head, when masking is used in the right ear, the tinnitus may move at most a little to the left. When the masking is applied to the left ear, the tinnitus may only shift to the right. This is where masking for both ears may produce the worst state, because then the patient hears three different sounds. He hears a masking sound in the left ear and another masking sound in the right ear, and he continues to hear a tinnitus sound in the head. Obviously, this arrangement is therefore not a solution, but this result does not mean that masking cannot work for this patient. The solution lies in using coherent sound emitted to both ears simultaneously, in which the masking sound should also be felt at the top of the head. It is generally accepted that the bone conduction stimuli in both ears are nearly equal, so that bone conduction masking of tinnitus located in the head can be attempted when appropriate. Perhaps bone conduction masking may work better.