Indian Journal of Otology

ORIGINAL ARTICLE
Year
: 2021  |  Volume : 27  |  Issue : 3  |  Page : 131--139

Impact of duration of residual inhibition on tinnitus masking in patients with and without hearing impairment


Indranil Chatterjee1, Geeta Gore2,  
1 AYJNISHD (Speech and Hearing), Kolkata, West Bengal, India
2 BYL Nair Hospital and T.N. Medical College, Mumbai, Maharashtra, India

Correspondence Address:
Mr. Indranil Chatterjee
AYJNIHH, NILD Campus, Bonhooghly, B.T. Road, Kolkata - 700 090, West Bengal
India

Abstract

Introduction: Residual inhibition (RI) is described as a temporary reduction in the loudness of tinnitus as a result of stimulation from a noise. Aim: This study is aimed to determine the efficacy of durational aspects of tinnitus masking on self-reported tinnitus handicapped measures in patients with and without hearing impairment. Sample Size: Sixty participants were included and divided into two groups – Group A (mean age 44.7, standard deviation [SD] 12.02) included tinnitus participants with normal hearing and Group B (mean age 43.81, SD 12.79) included participants with hearing impairment. Methodology: Audiological evaluation was done after a detailed case history visual analog scale (VAS) and tinnitus handicapped inventory (THI) were used pre- and post-therapy to assess the severity of tinnitus. Tinnitus masking was done at the level MML + 20 dB at matched frequency of the tinnitus. Each group had three subgroups of ten participants for masking duration– 15, 20, and 30 min of RI. The therapy was terminated when the tinnitus disappeared or after 1 month (5 days a week). Statistical analysis was performed using Paired t-test, Independent t-test, and ANOVA. Results: There was a significant difference in the effect of tinnitus masking for pre- and post-data among different masking durations measured in VAS and THI irrespective of hearing status. 30-min masking duration can be used as a standardized norm for tinnitus masking. Conclusion: Thus, the study provides a structured temporal course for providing tinnitus masking.



How to cite this article:
Chatterjee I, Gore G. Impact of duration of residual inhibition on tinnitus masking in patients with and without hearing impairment.Indian J Otol 2021;27:131-139


How to cite this URL:
Chatterjee I, Gore G. Impact of duration of residual inhibition on tinnitus masking in patients with and without hearing impairment. Indian J Otol [serial online] 2021 [cited 2022 Jan 26 ];27:131-139
Available from: https://www.indianjotol.org/text.asp?2021/27/3/131/332651


Full Text



 Introduction



Tinnitus can affect the entire life of an individual, can prevent intellectual work, and impair the quality of life in general.[1] Residual inhibition (RI) is the temporary suppression or elimination of tinnitus following acoustic stimulation.[2],[3] The method has been widely used and often considered as a mainstay of tinnitus treatment.[4] The basic principle of tinnitus masking is the after effect of sound presentation and not really the effects that happen during the sound. The range of masker duration recovery time is linearly related to the logarithm of masker duration. If masker duration increases, there is a linear increment in the recovery period, but it is not known what effect does masking has for a time period >10 min.

Need of the study

There are no controlled, randomized clinical studies that have documented the efficacy of tinnitus masking.[5] The purpose of testing for RI is to determine whether the use of tinnitus maskers would be a viable treatment course.[6] There is an immense need for developing an economical and durational viable tinnitus masking procedure by using a diagnostic pure tone audiometer to understand the period for its possible clinical benefits. The range of masker duration recovery time is linearly related to the logarithm of masker duration. If masker duration increases, there is a linear increment in the recovery period, but it is not known what effect does masking has for a time period >10 min. Thus, there is a need for further study to focus the therapeutic benefit on the temporal course of masking.[7] There is no information regarding the number of sessions for initial planning and cessation for tinnitus masking therapy mentioned in literature. The present need is for evidence demonstrating the durational efficacy of implementable methods of tinnitus treatment. This study may be exploratory research which may emancipate the efficacy of duration of tinnitus masking therapy for the tinnitus participants with hearing impairment and without hearing impairment.

Aim of the study

The aim of the study is to determine the efficacy of durational aspects of tinnitus masking on self-reported tinnitus handicapped patients with and without hearing impairment by using tinnitus masking through diagnostic pure tone audiometer.

Objectives

To compare the efficacy of tinnitus masking between 15 min, 20 min, and 30 min masking durations through pre-therapeutic data and post-therapeutic data based on a visual analog scale (VAS) and Tinnitus handicapped inventory (THI) score in tinnitus participants with hearing impairment.

 Methodology



Participants

The study was undertaken with a total of 60 participants (n = 60), selected from the clients reporting to the audiological department of AYJNISHD, ERC within the age range of 20–60 years. The participants were broadly divided into two groups – Group A included 30 tinnitus participants (mean age: 44.7, standard deviation [SD]: 12.02) with normal hearing and Group B included 30 participants (mean age: 43.81, SD: 12.79) with hearing impairment having mild to moderate degree of sensorineural hearing. None of the participants of Group B mentioned above were using any hearing aid or other type of amplification device due to issues like socioeconomic strata and/or cosmetic unacceptance and having tinnitus as their primary concern.

Inclusion criteria

Both male and female participants were selectedParticipants who were suffering from tinnitus unilaterally for at least last 6 months were included in this study.

Exclusion criteria

Participants with neurological disorder and cognitive impairment were excludedParticipants with phonophobia, misophonia, and hyperacusisParticipants using hearing aids The participants who had habits of daily intake of caffeine, quinine, aspirin, or any other drugs.

Methods

First, a detailed case history was obtained. Details of any significant history like vertigo, aural fullness and pressure fluctuations within the ear, fluctuations in hearing, ear pain or discomfort, tinnitus, and other physical complaints were carefully noted. The objective of the case history was to obtain as clear and complete profile in order to understand the lifestyle needs and problems of the patients. The clients had then undergone an audiological evaluation, including otoscopic examination, pure tone audiometry, and tympanometry and speech recognition thresholds.

The otoscopic examination was performed routinely to check for the presence of cerumen or any sign of infection in the external auditory canal or furuncle. The visibility of the tympanic membrane was noticed during otoscopic examination.

Pure tone audiometry was conducted as per ANSI[8] standards. TDH 39 headphones were used to measure thresholds from 250 Hz to 8000 Hz. The first tone is presented at the approximate most comfortable level (60 dB HL is appropriate to start). Pulse tone was used as the stimulus while conducting pure tone audiometry.[9],[10],[11],[12] Uncomfortable level was measured to assess whether there is hyperacusis.

Tympanometry was done to objectively rule out any middle ear pathologies. To determine acoustic Immittance, MAICO MI 44 Immittance audiometer was used. “A” type tympanogram was found for all the participants.

Speech Audiometry was performed by using Bangla phonetically balanced words[13] and Bangla spondee words.[14] The purpose of speech audiometry was to check for the reliability of the pure tone average.

Written consent of all participants was obtained as they are volunteered to take part in this experimental study of tinnitus.

Tools/instruments

THI developed by – Newman et al., 1996[15]Calibrated Diagnostic Audiometer (MAICO MA53) with TDH 39 earphones (according to manufacturer's standards)Immittance audiometer (MAICO MI 44, according to the manufacturer's standards)VAS.[16]

Procedure and statistical methods

Phase I

A detailed tinnitus interview was taken from each participant in which tinnitus-related information regarding duration and description of tinnitus was recorded along with written consent for participation in the study.

Phase II

Pre-therapy assessment

First VAS was used to estimate the severity of tinnitus, which consists of single 11-point Likert-like scale to assess tinnitus severity (0 means no tinnitus whereas 10 reveals the most severe tinnitus).

Then, the next measurement was done using tinnitus handicap inventory[15] to assess the participant's perceived severity of tinnitus. The THI is a self-administered, 25 – item questionnaire that is scored on a 3-point scale (No = 0, Sometimes = 2 and Yes = 4). The total THI score is the sum of the scores for the following three subclasses: functional, emotional, and catastrophic. Handicap severity can be categorized based on the THI index score as follows:[17]

Severe (58–100)Moderate (38–56)Mild (18–36)No handicap (0–16).

The presentation order of the two tests (VAS and THI) was the same for all participants.

Phase III

Psychoacoustic assessment: Assessment of tinnitus masking includes

Pitch matchingLoudness matchingMinimal masking levelsMeasure of RI.[2],[18]

This method was conducted for both groups.

Tinnitus pitch and loudness matching procedure[19] was done by General Testing Strategy for Tinnitus Matching using MAICO MA 53 audiometer. Prior to testing, the tinnitus ear and the stimulus ear were identified. The stimulus was presented in this stimulus ear, and the participants were instructed to compare with the tinnitus in the contralateral ear.[20],[21],[22]

The stimulus was generated by calibrated MAICO MA53 diagnostic pure tone audiometer with TDH 39 headphones. The intensity of masking stimulus was controlled by attenuator. All the participants were given minimal instruction and no counseling. Both Group A and B were subdivided into further three subgroups A.1, A.2, A.3 and B.1, B.2, B.3 respectively, where the participants were randomly selected as follows:

Group A.1-10 participants were given tinnitus masking for 15 min daily[23]Group A.2-10 participants were given tinnitus masking for 20 min daily[7]Group A.3-10 participants were given tinnitus masking for 30 min daily[24]Group B.1-10 participants were given tinnitus masking for 15 min daily[23]Group B.2-10 participants were given tinnitus masking for 20 min daily[7]Group B.3-10 participants were given tinnitus masking for 30 min daily.[24]

Phase V

The therapy was terminated when the tinnitus disappeared or given for a maximum of 1 month. The same standardized methods were used to assess post-therapy effects.

Phase VI

To investigate the objectives of the present study, all the statistical analyses were performed using the Statistical Package for the Social Sciences version 17 Software (IBM, Chicago, USA). The mean and SD was calculated for further analysis. Pair t-test, Independent t-test for mean values, and analysis of variance (ANOVA) was used with the significance level set at 95%. While testing the validity of the hypotheses, equal variances for the two groups were assumed.

 Results



Seventy-three tinnitus participants with tinnitus were screened. Among them, 13 failed to meet the criteria for inclusion. Sixty participants were broadly divided into two groups– Group A and Group B. Group A included thirty tinnitus participants with normal hearing and Group B included thirty participants with hearing impairment having mild to moderate degree of sensorineural hearing loss (pure tone thresholds was within 50 dBHL for both the ears). Both male and female participants were selected. Among all tinnitus participants, 38 participants were male and 22 participants were female. After taking a case history, audiological evaluation including pure tone audiometry, tympanometry, and speech audiometry were performed for both the groups, results of which are shown in [Table 1].{Table 1}

As mentioned earlier only, participants with unilateral tinnitus were included for this study. It was found that 34 participants had tinnitus in the left ear and 36 participants had in the right ear.

Thus, the overall results indicated that there was a significant difference between the pre and post-therapeutic condition of tinnitus masking measured in THI score for each group with reference to masking duration, thereby rejecting the null hypothesis [Table 2].{Table 2}

It can be inferred from the results of one-way ANOVA that there was a significant difference of posttherapy in VAS of the tinnitus participants with hearing impairment for the different groups with reference to various masking durations. Multiple comparison using the Tukey test also suggested that there was a significant difference in post-therapy data measured in VAS between the two groups with reference to 15 min and 20 min durations of tinnitus masking and between the groups with reference to 15 min and 30 min durations of tinnitus masking.

The results of one-way ANOVA of pre-therapy VAS [Table 3] for the three groups with reference to durations – 15 min, 20 min, and 30 min for tinnitus participants without hearing impairment depicted that there was no significant difference in pre-therapy VAS. Multiple comparison using Tukey also suggested the same. VAS also suggested that the participants were randomly selected.{Table 3}

The results of one-way ANOVA of post-therapy VAS [Table 3] for the three groups with reference to and without durations – 15 min, 20 min, and 30 min for tinnitus participants without hearing impairment depicted there was a significant difference Multiple comparisons using Tukey test indicated that although there was no significant difference between 20 min and 30 min masking durations, but there was a significant difference between 15 min and 20 min masking durations and also between 15 min and 20 min masking durations. Thus the null hypothesis (H0) was rejected and the presumed hypothesis that there would be a significant difference in the effect of tinnitus masking between 15 min, 20 min, and 30 min masking duration measured in VAS for the tinnitus participants without hearing impairment was accepted.

Independent t-test [Table 3] was done to calculate the significance level and the presence or absence of any significant difference between tinnitus with and without hearing impairment regarding tinnitus masking therapy with reference to difference tinnitus masking durations (15 min, 20 min, and 30 min).

Independent t-test revealed that there was no significant difference between the pre-therapy VAS of participants with hearing impairment and without hearing impairment and post-therapy VAS for participants with and without hearing impairment thereby accepting the null hypothesis and rejecting the presumed hypothesis that there would be a significant difference in the effect of tinnitus masking for pre- and post-therapeutic data between 15 min, 20 min, and 30 min masking durations measured in VAS when compared between tinnitus with and without hearing impairment as the P < 0.05 was rejected.

The results of one-way ANOVA of pre-therapy THI score [Table 4] for the three groups with reference to masking duration – 15 min, 20 min, and 30 min for tinnitus participants with hearing impairment showed no significant difference in the pre-therapy data. Multiple comparison using Tukey also suggested the same. This interpretation indicated that the participants having tinnitus with hearing impairment for the different groups with reference to durations for tinnitus masking were randomly selected for specific tinnitus masking durational periods.{Table 4}

The results of one-way ANOVA of post-therapy THI score for these three groups with reference to masking durations showed no significant difference of post-therapy data on THI score of the tinnitus participants with hearing impairment for the different groups with reference to tinnitus masking duration. Multiple comparison using Tukey test also showed the same. The null hypothesis (H0) was accepted, and the presumed hypothesis that there would be a significant difference in the effect of tinnitus masking between 15 min, 20 min, and 30 min masking duration measured in THI score for the tinnitus participants with hearing impairment was rejected.

The one-way ANOVA of pre-therapy THI score for the three groups with reference to masking durations – 15 min, 20 min, and 30 min were depicted for tinnitus participants without hearing impairment showed no significant difference. Multiple comparison using Tukey showed no significant difference in pre-therapy THI score for each pair of groups with reference to masking durations indicating that the participants were randomly selected.

The results of one-way ANOVA of post-therapy THI score for the three groups with reference to masking durations – 15 min, 20 min, and 30 min null hypothesis (H0) was accepted, and the presumed hypothesis that there would be a significant difference in the effect of tinnitus masking between 15 min, 20 min, and 30 min masking duration measured in THI score for the tinnitus participants without hearing impairment was rejected.

The overall results indicated that there was no significant difference of pre-therapy THI scores between participants with hearing impairment and without hearing impairment.

The mean values of the posttherapy THI score (see [Table 2]) for different groups with reference to masking durations derived from tinnitus participants with and without hearing impairment showed significant differences on comparison, and the null hypothesis was rejected. The presumed hypothesis there would be a significant difference in the effect of tinnitus masking for pre- and post-therapeutic data for different masking duration groups (between 15 min, 20 min, and 30 min) between with and without hearing impairment was accepted.

 Discussion



Ipsilateral masking was used as it is more effective than contralateral masking.[7] Comparison between the two conditions was made by administering paired t-test. The present study was undertaken to ascertain that there would be a significant improvement of the effect of tinnitus masking therapy for each group with reference to duration of tinnitus masking while comparing pre and post-therapeutic data. Paired t-test revealed that the impact of tinnitus as measured by THI score were significant (P < 0.05) for all the participants among each group. Hazell et al.[25] also supported this concept as he reported that users found sound therapy devices subjectively helpful and reported lower levels of tinnitus annoyance with their use. Vernon and Meikle[22] have also described instances where patients first had the experience of silent ears after providing tinnitus masking therapy. These results supported that tinnitus masking therapy is an effective technique for the amelioration of tinnitus.[26] Hence, the use of tinnitus masking therapy provides not only temporary relief but also long-term effects as it improves the quality of life[27] and it is one of the most employed therapeutic methods and one of the most beneficial for patients suffering from tinnitus.[28] Banks (2003)[33] used 15 min duration using pure tone, warble, and narrowband noise once or twice a week for 3 weeks and compared pre and post effects through tinnitus handicap questionnaire and reported about 12% improvement in the social, emotional and behavioral domain, 8% in tinnitus and hearing and 7% in outlook. The comparison from this study supports the findings that 15 or 20 min duration can be considered too small to yield effective results in tinnitus suppression through RI. Struve (2007)[34] used 30 min duration narrowband noise in combination with a neuro-suppressor pregabalin to decrease central nervous system hyperactivity. Hazel and Wood[23] showed that 15 min of masker use is enough to produce RI, and lesser durations could also work while raising the masker levels. However, in some cases, with the problem of tolerance to the masker, longer durations are required at low masker levels. This can lead to the implementation of long duration maskers for patients with tolerance problems at high masker levels, which can be a crucial finding from this study.

Comparison of tinnitus masking effect between three groups with reference to various masking durations

The duration of tinnitus masking session is the discretion of individual audiologists and varies in a wide range in different audiological settings. Hazell and Wood[23] used 15 min masking duration for the patients having tinnitus. For three subjects having tinnitus 20 min masker was presented in another study.[7]

There is no study regarding the detailed masking temporal course of tinnitus participants to provide the maximum benefit. So, providing tinnitus masking therapy should be concerned with the duration of tinnitus masking. As already stated previously, the task of this study was to find whether there is any significant difference between the three groups with reference to durations of tinnitus masking in participants having tinnitus on VAS and tinnitus handicapped inventory. One-way ANOVA was administered to compare the durational efficacy between three groups with reference to masking duration (15 min, 20 min, and 30 min) for the tinnitus participants with and without hearing impairment. Multiple comparisons between three groups with reference to masking durations were compared on both THI score and VAS. On analyzing the improvement patterns of three groups with reference to masking duration for the tinnitus participants without hearing impairment shows tinnitus masking for 15 min is better than tinnitus making for 20 min and 30 min for VAS. Similar result was found for the participants having tinnitus with hearing impairment. However, it was observed that there was no significant difference on THI score between post tinnitus masking therapeutic data of 20 min and 30 min masking durations for the tinnitus participants having hearing impairment as well as for the tinnitus participants without hearing impairment.

Longer durations >30 min were not studied in this study, so conclusive evidence could not be provided that duration of more than 30 min does not have any impact on relief provided by tinnitus. Roberts et al. (2008)[35] studied the overlap of the tinnitus spectrum and the frequency. Their findings suggested that RI of tinnitus depends upon the affected hearing frequency range, which can mean that the duration of 30 min found best in this study can be variable in individuals with varying hearing loss. However, 30 min duration shows improvements in both hearing impaired and normal hearing subjects both in a similar pattern. Longer masking durations can be a viable tool for cases with tolerance problems at high masker levels. Combining long durations with low masker levels may yield similar results to shorter durations with higher masker levels but may be useful for cases with tolerance problems at higher levels.

Comparison of the effect of tinnitus masking with reference to various durations between tinnitus with and without hearing impairment

Individuals with tinnitus often have hearing loss, but tinnitus may also occur, although rarely, in individuals with normal or near-normal hearing.[1] The patients with tinnitus and normal hearing lies between a range from 7.4% to 20%.[29] The severity of tinnitus was found to be independent of type and degree of hearing loss.[30]

As already stated previously the task of this study was to find whether there is any significant difference in the effect of tinnitus masking for pre and post-therapeutic data between 15 min, 20 min and 30 min durational procedures measured in THI score and VAS when compared between tinnitus with and without hearing impairment.

Although the physiology related to the effect of tinnitus masking in tinnitus participants with and without hearing impairment is not clear, there are indications that nonauditory regions of the brain are also activated abnormally in some forms of subjective tinnitus.[31] Although the exact neural mechanisms regarding the effect of tinnitus masking is not well understood it can be assumed that the fact that tinnitus can be masked suggests that the tinnitus and the response to the acoustic stimulus share the same neural channels somewhere in the nervous system. When this masking occurs, it is assumed that the excitation pattern of the masker has overlapped with that of the signal.[32] Hence, neuro-imaging guided studies are needed to concretely state whether the above mention regions are affected or not. It is also the need of the hour to specify region-specific tinnitus affect to help in further tinnitus management.

 Conclusion



Thus, the study provides a structured temporal course for providing tinnitus masking therapy for normal hearing tinnitus participants as well as for tinnitus participants with hearing impairment. Thirty minutes masking duration can be established as the norm for running tinnitus clinic as it is the balanced time duration in all aspects, neither too long nor too short. This is the first study to observe RI solely by varying masker durations without any pharmacological or electrical stimulation for tinnitus suppression.

Although tinnitus masking is a critical element for tinnitus treatment, and the results suggest that diagnostic pure tone audiometer can be used as noise generator due to its cost-efficacy, and it can be an economically viable option. However, study with different sound generators has not been conducted. Thus, 30 min masking duration can be used to treat patients with tinnitus not only using audiometer but also masker and other sound enrichment devices. Further Standardization of the 30 min masking duration as a treatment norm for treating tinnitus in normal and hearing-impaired population, modulated noise, and masking noise can be used in the form of software. The above-synthesized noise can further be used by tinnitus patients easily through an Android phone, pen drive, etc. Although there is still considerable uncertainty regarding the mechanism responsible for such effects, the data gathered here has shown that the improvement on subjective scale (THI and VAS) is dependent on the duration of the stimulus of tinnitus masking. The present study focuses on the durational efficacy of tinnitus masking. The research provides evidence of relationships of effect of tinnitus masking with reference to durational aspects between hearing-impaired tinnitus participants and normal hearing tinnitus participants.

Windows for further research

By trial and error standard and comprehensive audiological practice of tinnitus masking at different intensity level should be establishedFollow-up is essential to assess long-term benefit of tinnitus masking with reference to durationLarger sample size with equal proportions of males and females may be considered so as to generalize the outcome evaluation depending upon larger dataThe most successful treatment programs of tinnitus include multimodal strategies that are designed to address the specific need of each patient. Interdisciplinary approach with collaborative effort should be used in more detail for acclimatization of effectivenessFurther study should be designed to ensure by establishing the tinnitus masking of the least effective masking durationf-MRI, PET-guided assessment is needed. That will be a more comprehensive approach to test the potential of tinnitus masking. Human imagining should be conducted to know the changes in the balance of excitatory and inhibitory inputs in the central auditory system as well as the connection between the amygdala and emotional response in nonclassical pathway as an effect of tinnitus masking. Furthermore, electrophysiological tests should be conducted to assess therapeutic outcomes appropriately.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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