Minimum Masking Level Research Articles

Evaluating psychoacoustic measures for establishing presence of tinnitus

The Department of Veterans Affairs (VA) considers tinnitus a disability. Veterans can claim tinnitus as a "service-connected" disability if the tinnitus is thought to be connected to military service. The VA adjudicates each claim and determines whether reasonable evidence exists to support it. Currently, determining the presence of tinnitus is based on subjective reporting-objective measures do not exist. The aim of this study was to develop and document a test for detecting the presence/absence of tinnitus with high confidence. Using our computer-automated, self-guided tinnitus evaluation system, we conducted three phases of testing to compare psychoacoustic measures of tinnitus between participants with versus without tinnitus. Phase 1 measures included loudness match, pitch match, minimum masking level, residual inhibition, Békésy, and forced-choice double staircase. Phases 2 and 3 measures were chosen based on results of the previous phase. The number of tests and time of testing decreased during each successive phase. Differences were seen between groups; most notably, higher low-frequency loudness matches and higher median pitch matches were observed for participants with tinnitus. Results of this study suggest that further efforts can produce a defined psychoacoustic test battery for identifying the presence/absence of tinnitus.

Characterisitics and maskability of self-reported tinnitus in adult Nigerians.

Tinnitus or noise perception with no identifiable acoustic origin is a perplexing symptom to sufferers as well as to otolaryngologists saddled with managing such patients. With most studies from the continent focusing on etiologies and clinical types, there is paucity of information on psychoacoustic properties of tinnitus among Africans. Tertiary care otolaryngology clinics in Abuja. To determine characteristics and maskability of tinnitus seen in adult Nigerians who self-report tinnitus as the main presenting symptom. A prospective study involving 100 adult Nigerians seen at two specialist Otorhinolaryngology clinics in Abuja - National Hospital Abuja and CSR Otologics Specialist Clinics, Abuja between January 2008 and June 2014. Clinical and audiological history and findings were captured in the study protocol. Participants were then assessed to determine Tinnitus pitch match, loudness match, mask ability and minimum masking level as well as residual inhibition. 100 participants aged 24 - 58 years were assessed. Male to female ratio was 1:1.4. Tinnitus was sudden in onset in 24%, and gradual in 76%, involved the right ear in 32%, left ear in 38% and both ears in 30%. 48% of participants have other symptoms apart from tinnitus, and 32% were on other medications known to induce tinnitus. 16% of participants gave history of exposure to significant loud sound. Only 16% of participants have significant otoscopic findings. Tinnitus abated with carotid pressure in 64%, with extra ocular muscle movement in 16%, with teeth clenching in 32%, with neck movement in 28%, and with movement of arms or legs in 8%. The mean difference in hearing threshold of ear with and without tinnitus was 12.09 dB HL. Tinnitus pitch match was 4 KHz in 44%, 3 KHz in 24%, and 2 KHz in 32%, while mean tinnitus loudness match was 41.24 dB SL. Tinnitus was maskable in 88% of subjects, with a residual inhibition of 2 to 76 seconds. Majority of adult Nigerians that self-report tinnitus have maskable tinnitus, and this should be considered when considering hearing augmentation for those with associated impaired hearing.

METHOD AND APPARATUS FOR TINNITUS EVALUATION

Methods, articles of manufacture, and systems for evaluating tinnitus are disclosed herein. According to various embodiments, a tinnitus evaluation system may include a tinnitus evaluation module configured to perform one or more tinnitus evaluation tests. A tinnitus evaluation test may comprise generating a first single-frequency sound based at least in part on a sound of a patient's tinnitus, and generating a narrow-band sound centered at the frequency of the first single-frequency sound. Tests include a hearing threshold test, a loudness match test, a pitch match test, a bandwidth match test, a minimum masking level test, and a residual inhibition test.

A randomized, double-blind, placebo-controlled clinical trial to evaluate the efficacy and safety of neramexane in patients with moderate to severe subjective tinnitus

BackgroundNeramexane is a new substance that exhibits antagonistic properties at α9α10 cholinergic nicotinic receptors and N-methyl-D-aspartate receptors, suggesting potential efficacy in the treatment of tinnitus.MethodsA total of 431 outpatients with moderate to severe subjective tinnitus (onset 3-18 months before screening) were assigned randomly to receive either placebo or neramexane mesylate (25 mg/day, 50 mg/day and 75 mg/day) for 16 weeks, with assessment at 4-week intervals. The primary (intention-to-treat) efficacy analysis was based on the change from baseline in Week 16 in the total score of the adapted German short version of the validated Tinnitus Handicap Inventory questionnaire (THI-12).ResultsCompared with placebo, the largest improvement was achieved in the 50 mg/d neramexane group, followed by the 75 mg/d neramexane group. This treatment difference did not reach statistical significance at the pre-defined endpoint in Week 16 (p = 0.098 for 50 mg/d; p = 0.289 for 75 mg/d neramexane), but consistent numerical superiority of both neramexane groups compared with placebo was observed. Four weeks after the end of treatment, THI-12 scores in the 50 mg/d group were significantly better than those of the controls. Secondary efficacy variables supported this trend, with p values of < 0.05 for the 50 mg/d neramexane group associated with the functional-communicational subscores of the THI-12 and the assessments of tinnitus annoyance and tinnitus impact on life as measured on an 11-point Likert-like scale. No relevant changes were observed for puretone threshold, for tinnitus pitch and loudness match, or for minimum masking levels. The 25 mg/d neramexane group did not differ from placebo. Neramexane was generally well tolerated and had no relevant influence on laboratory values, electrocardiography and vital signs. Dizziness was the most common adverse event and showed a clear dose-dependence.ConclusionsThis study demonstrated the safety and tolerability of neramexane treatment in patients with moderate to severe tinnitus. The primary efficacy variable showed a trend towards improvement of tinnitus suffering in the medium- and high-dose neramexane groups. This finding is in line with consistent beneficial effects observed in secondary assessment variables. These results allow appropriate dose selection for further studies.Trial RegistrationClinicalTrials.gov NCT00405886

Thickness of the Human Round Membrane in Ménière's Disease

RESULTS: The population mean age was 51.48 15. 44.26% of the patients were males. 58.83% of the patients identify the tinnitus as a pure tone sound. Bilateral tinnitus was found in 79 (43.17%) patients. 54 (29.50%) patients had right tinnitus, and 50 (27.33%) left tinnitus. The associated pathologies were presbycusis (39.34%), sudden deafness (10.93%), acoustic trauma (7.65%), primary hydrops (4.37%), otosclerosis (4.37%), meningioma (1.04%), acoustic neuroma (1.04%), and temporal bone fracture (0.55%). In 4.92% of the patients we could not identify the cause. 25.68% of the patients had normal pure tone and speech audiometry. The equiparation volume media of tinnitus was 6.2db over pure tone threshold. The minimal masking level media was 11.9db pure tone threshold. CONCLUSION: The mean age of the affected population was 51.52 /- 15. The three most common etiologies of tinnitus in this population were presbycusis, deafness and acoustic trauma. Tinnitus was also found in a group of patients with normal hearing. Tinnitus was identified as a pure tone sound in almost a half of the population, and frequently compromised both ears.

Tinnitus Evaluation and Intervention

You have accessThe ASHA LeaderBottom Line1 Mar 2009Tinnitus Evaluation and Intervention Steven WhitePhD, CCC-A Steven White Google Scholar More articles by this author , PhD, CCC-A https://doi.org/10.1044/leader.BML.14032009.3 SectionsAbout ToolsAdd to favorites ShareFacebookTwitterLinked In Audiologists often call ASHA with questions on coding and reimbursement for audiological services involving tinnitus evaluation and intervention. The following Q&A answers the most common questions. Q: Which International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes should be used for tinnitus? ICD-9-CM 2009 codes for tinnitus are 388.30: tinnitus, unspecified; 388.31: subjective tinnitus; and 388.32: objective tinnitus. Q: Which Current Procedural Terminology (CPT)® code should be used for tinnitus assessment? Use CPT code 92625: assessment of tinnitus (includes pitch, loudness matching, and masking). Q: What are these tinnitus assessment components? Pitch (frequency) matching is intended to match the stimulus closest in pitch to the patient’s tinnitus. Loudness matching testing is performed to obtain loudness matches between the audiometric stimulus and the patient’s tinnitus. The masking procedure involves determination of the minimum masking level (MML) and testing for tinnitus suppression (residual inhibition). If only one ear is tested using the tinnitus assessment procedure, the modifier -52 (reduced service) should be applied. This modifier would also be used if only part of the tinnitus assessment battery is performed. Q: Which CPT code should be used when evaluating a client with a tinnitus masker? You can consider using CPT 92590 (hearing aid examination and selection: monaural) or 92591 (hearing aid examination: binaural). Q: How do I code the masker itself? A tinnitus masker could be coded using Level II Health Care Procedure Coding System National Codes (HCPCS), which are required for reporting most medical services and supplies provided to Medicare and Medicaid patients and by most private payers. There is not a code for a tinnitus masker, but V5299 is for hearing service, miscellaneous. HCPCS instructions note that this code should be used only if a more specific code is unavailable. Hearing services fall under V5000–V5999. Q: Can the various interventions used for the treatment of tinnitus be reimbursed? Most third-party payers view tinnitus treatment claims based on the procedure. For example, Aetna’s Clinical Policy Bulletin 0406 states that Aetna considers transcutaneous electrical nerve stimulation (TENS) medically necessary durable medical equipment (DME) for members with severe tinnitus when all of the following criteria are met: “(1) Member has experienced severe tinnitus for more than 6 months, and (2) Medically correctable causes of tinnitus have been ruled out, and (3) Member has tried and failed conservative tinnitus treatments, including counseling and reassurance, dietary modifications, and drug therapy.” Aetna limits coverage to no more than 10 TENS sessions per year “because of a lack of evidence that more frequent TENS treatments provides additional clinically significant benefits for this condition.” Aetna denies coverage for tinnitus instruments, ear canal magnets and electromagnetic stimulation, and tinnitus retraining therapy because they are experimental, investigational, or the effectiveness has not been established. Medicare will cover a tinnitus evaluation performed by an audiologist if the patient is referred by a physician. However, Medicare states in its Coverage Issues Manual that tinnitus masking is considered “an experimental therapy” and does not cover that procedure. Q: Is there no specific CPT code for tinnitus intervention? That’s correct. There is no such code. For tinnitus intervention you can consider using 92507: treatment of speech, language, voice, communication, and/or auditory processing disorder, individual. CPT code 92633: auditory rehabilitation, postlingual hearing loss, does not include tinnitus intervention. Q: Where can I find more information about CPT codes and HCPCS? A good place to start is the ASHA Web page on billing and reimbursement; it includes a specific section on coding. The American Medical Association (AMA) CPT and HCPCS books are available through the AMA Press. The Coders’ Desk Reference, designed for the lay person, is available through Ingenix Companies (800-765-6588). ASHA’s Private Health Plans Handbook also has a list of the CPT codes commonly used by members, and is available through ASHA Product Sales. Author Notes Steven White, PhD, CCC-A, director of health care economics and advocacy, can be reached at [email protected]. Advertising Disclaimer | Advertise With Us Advertising Disclaimer | Advertise With Us Additional Resources FiguresSourcesRelatedDetails Volume 14Issue 3March 2009 Get Permissions Add to your Mendeley library History Published in print: Mar 1, 2009 Metrics Current downloads: 2,158 Topicsasha-topicsleader_do_tagasha-article-typesleader-topicsCopyright & Permissions© 2009 American Speech-Language-Hearing AssociationLoading ...

Transmeatal Low-Level Laser Therapy for Chronic Tinnitus with Cochlear Dysfunction

Objectives: To establish the efficacy of low-level laser therapy for tinnitus. Methods: We performed a prospective, randomized double-blind study on 60 outpatients with tinnitus presenting sensorineural hearing loss in the affected ear. They were randomly divided into two groups, the first performing active laser therapy 20 min a day for 3 months with a 650-nm, 5-mW soft laser (group L), the second using a dummy device which duplicated all aspects of active laser therapy except for the activation of the laser beam (group C). One subject in both groups dropped out due to an increase in tinnitus loudness. Two more patients in each group ceased to comply with the protocol due to familiar problems. Results: The Tinnitus Handicap Inventory (THI) was considered the main outcome measure; no statistical difference was detected between the 2 groups in the THI total score (p = 0.97), and its functional (p = 0.89), emotional (p = 0.89) and catastrophic (p = 0.89) subscales. Moreover, a visual analog scale for self-perceived loudness of the tinnitus showed no difference between the groups (p = 0.69). Regarding psychoacoustic parameters, the minimum masking level showed no difference (p = 0.42), while loudness expressed in sensation level exhibited lower values in group L (p = 0.0127). Group L subjects also presented a decreased rate of hyperacusis (p = 0.02). No changes were detected in the audiometric threshold in both groups. Conclusions: Soft laser therapy demonstrated no efficacy as a therapeutic measure for tinnitus.

Tinnitus Suppression Using AM and FM Acoustic Stimuli

Objective 1) Customize amplitude-modulated (AM) and frequency-modulated (FM) acoustic stimuli to suppress tinnitus. 2) Understand the theoretical mechanisms underlying tinnitus suppression. Methods A double-staircase adaptive procedure was utilized to match both the frequency and intensity of the tinnitus. Minimal masking levels for both noise and pure tones were acquired. In a double-blinded procedure, sinusoidally amplitude- and frequency-modulated stimuli were administered. Pre- and post-stimulation tinnitus loudness levels were compared to quantify the effects of suppression and residual inhibition of tinnitus. Multivariate analysis was performed to evaluate independent predictors of tinnitus suppression. Different types and severity of tinnitus and hearing loss were correlated with the effective sounds. Results At present, 18 patients aged 35 to 75 (mean 58.3) with Tinnitus Handicap Index (THI) scores ranging from 12 to 90 (mean 52.6) have been evaluated. Significant associations were found between the duration of the AM and FM stimuli and the effect on tinnitus suppression. 10 out of 18 (56%) patients had a reduction in their tinnitus loudness by 30% or more. Upon comparison with the masking level, reduction in the subjects’ tinnitus was observed when a lower intensity of the modulated stimuli was presented. Subject characteristics that correlated with a significant reduction of the tinnitus will be discussed in detail. Conclusions AM and FM stimuli can decrease the percept of tinnitus significantly. It is postulated that AM and FM stimuli produce synchronized cortical responses to more efficiently compete against tinnitus-induced synchrony.

Feasibility of Auditory Cortical Stimulation for the Treatment of Tinnitus

To investigate the feasibility and safety of an implantable epidural cortical stimulator for the treatment of severe tinnitus. Prospective, controlled, single-blinded study of cortical stimulation for 4 weeks, and then an open-label stimulation period. Tertiary care referral center. Adults (n = 8) with constant tinnitus of at least 1 year with a tinnitus reaction questionnaire score greater than 33. Tinnitus was predominantly unilateral with a frequency less than 8,000 Hz. Surgical implantation of an investigational epidural electrode over the posterior superior temporal gyrus using functional magnetic resonance imaging targeting. A 2-week stimulation period alternated with a 2-week sham period in random order to which subjects were blinded. This was followed by continuous stimulation with parameter adjustments to maximize tinnitus suppression. Subjective rating of tinnitus severity, loudness, and device efficacy. Objective measures of hearing thresholds, tinnitus frequency, loudness, and minimum masking levels. Outcome measures using the Tinnitus Handicap Questionnaire, Tinnitus Reaction Questionnaire, and Beck Depression Inventory. There were no effects of stimulation during the 4-week blinded period. With continuous chronic stimulation, 2 patients had persistent reduction of pure-tone tinnitus, and 6 patients had short periods of total tinnitus suppression. Significant improvements in the Beck Depression Inventory and tinnitus questionnaires were found, although objective measures of tinnitus loudness remained fairly stable. No surgical or stimulation-related complications were noted. Chronic electrical stimulation of the secondary auditory cortex seems safe and warrants further investigation as a potential therapeutic intervention for the suppression of tinnitus.

Neuromonics Tinnitus Treatment: Third Clinical Trial

The Neuromonics Tinnitus Treatment combines the use of a novel approach to acoustic stimulation with a structured program of counseling and support by a clinician specifically trained in tinnitus rehabilitation. The distinctive acoustic component has been designed to provide stimulation to auditory pathways deprived by hearing loss, engage positively with the limbic system, and allow intermittent, momentary tinnitus perception within a pleasant and relaxing stimulus, thereby facilitating desensitization to the tinnitus signal. The purposes of this study were (1) to demonstrate the efficacy of the treatment, when enhanced with various modifications since previously reported trials and (2) to test the relative clinical effectiveness of two variations of the approach. In the first, intermittent tinnitus perception was facilitated throughout treatment through the use of a stimulus in which intensity peaks allowed the patients' tinnitus perception to be completely covered up, whereas in the intensity troughs their tinnitus was briefly discernible. In the second, subjects experienced little tinnitus perception while listening to the treatment for the first 2 mo, then experienced intermittent perception. Thirty-five subjects with a predominantly moderate to severe level of tinnitus-related distress before treatment were randomly allocated into one of two treatment groups, corresponding to the two stage-based variations of the Neuromonics Tinnitus Treatment. Participants were provided with a high-fidelity personal sound player with earphones and an acoustic stimulus that had been spectrally modified according to their individual audiometric profile. They were instructed to use the acoustic stimulus for at least 2 hr per day, particularly at those times when their tinnitus was usually disturbing. Each group had equal amounts of clinician time for education, monitoring, and support. At 2, 4, 6, and 12 mo after commencing treatment, both groups displayed clinically and statistically significant improvements in tinnitus distress, awareness, and minimum masking levels as well as loudness discomfort levels. Improvements increased with time over the first 6 mo of therapy, at which time 91% of all subjects across the two groups reported an improvement in tinnitus disturbance (as measured by the Tinnitus Reaction Questionnaire) of at least 40%, with a mean improvement of 65%. Also, 80% of subjects at 6 mo reported a level of tinnitus disturbance that was no longer clinically significant. There was some indication of a more consistent benefit over 12 mo for the group that was provided initially with a high level of tinnitus interaction; however, inter-group differences were not statistically significant. A relation between reported treatment usage (hours per day) and clinical outcomes was observed, suggesting that a "dosage effect" may apply with the stimulus provided. This study found that the Neuromonics Tinnitus Treatment provides rapid and profound improvements to the severity of tinnitus symptoms and their effect on the subject's quality of life. This was a consistent effect, provided by a treatment that subjects reported as being pleasant to use. Both of the stage-based variations of the treatment that were tested in this study were shown to be successful in achieving these outcomes.

Assessment of Objective Pulsatile Tinnitus in a Patient with Syringohydromyelia

We examined a 38-year-old male with syringohydromyelia and concomitant symptoms suggestive of intracranial hypertension including unilateral low-frequency sensorineural hearing loss and objective pulsatile tinnitus. The tinnitus was heard by the authors (through a hearing aid stethoscope tube), measured objectively (with a probe microphone), measured subjectively (as minimum masking levels and with fixed frequency Bekesy), and altered by changes in ear canal pressure (subjectively reported and measured objectively with a probe microphone). The audiologic symptoms were likely associated with elevated cerebrospinal fluid pressure that traveled to the cochlea through the cochlear aqueduct. The tinnitus may have originated from pulsations of central vascular structures that traveled through the cochlear aqueduct or the endolymphatic duct. Hearing loss likely resulted from tinnitus masking or a stiffening of the cochlear partition or stapes footplate.

Evaluation of the Mixing Point in Tinnitus Sound Therapy by a Psychoacoustic Matching Protocol with a Digital Tinnitus Evaluation System

Directive counseling and sound therapy have been reported to effectively alleviate tinnitus suffering. Without objective evaluation, researchers doubt the real effect of sound therapy. This study was designed to evaluate the frequency and intensity of the theoretical ‘mixing point’ (MP) in sound therapy and to investigate its relationship with the minimal masking level (MML) of tinnitus. The tinnitus tones of 133 patients were successfully matched in frequency (dominant in 4–10 kHz) and loudness (83.09 ± 12.04 dB) using a psychoacoustic matching protocol and a newly designed tinnitus evaluation system. The matching rate was 83%. The relationship between the MP and MML is described by a linear regression equation: MP = 0.90 × MML + 1.98 (r² = 0.82, p < 0.0001). The results of matching and correlation analysis confirmed the consistency of the MP in sound therapy. The psychoacoustic characteristics of tinnitus can be objectively evaluated with our matching protocol and evaluation system.

New instrumentation for automated tinnitus psychoacoustic assessment

Conclusion: Although tinnitus is a major health problem, techniques to quantify its perceptual aspects are not standardized. This study represents a key step in our efforts to develop clinical methodology to accurately and reliably quantify the sensation of tinnitus, using a uniform method for obtaining a battery of tinnitus measures. Objectives: The purpose of this study was to evaluate the performance of the automated system, which was redesigned to reduce time of testing and to add new testing capabilities. The primary difference in function was the use of a ‘knob’ device that enabled patient control of auditory stimuli. The new tests included assessment of minimum masking level (MML) and residual inhibition (RI). Materials and methods: As with previous iterations of the system, a computer program ran all testing and subjects read instructions and provided responses via a computer touch-screen. Three separate studies were conducted. Study 1 evaluated within- and between-session test-retest response reliability of tinnitus loudness matches (LMs) and pitch matches (PMs). Study 2 was conducted to evaluate differences in LMs and PMs between subjects with and without tinnitus – to obtain pilot data to assist in the development of a test for ‘tinnitus malingering.’ Study 3 evaluated the system's capability of obtaining MMLs and RI as well as the between-session reliability of these measures. Results: Study 1 documented that the new system could obtain LMs and PMs within ∼20 min, while maintaining clinically acceptable reliability. Study 2 revealed characteristic differences in LM and PM test results for individuals who did not experience tinnitus. Study 3 documented the system's ability to obtain measures of MML and RI that were reliable across sessions.

Tinnitus neural map; A positron emission tomography study

The neural map of tinnitus involves more than the classical auditory pathways and the limbic system. PET findings in six patients, with severe problem tinnitus, revealed the involvement of the cerebellum, insula and frontal cortices when these patients were imaged before and after high frequency bone conduction therapy. The frontal cortex and cerebellum demonstrated the highest ratios of metabolic change but changes were also noted in the thalamus and the medial temporal lobe system. The PET data supports the view that the frequency specific map of auditory cortex is dynamic and can change with high frequency therapy, presumably due to neural reorganization. The PET data further reflect alterations in multiple areas of brain in all patients to tinnitus and/or high frequency therapy. Encouraging was the observation that patients with the most dramatic change in their global pre/post PETs were also the ones who exhibited the greatest behavioral improvement in regards to tinnitus relief measured by informal report and standard questionnaires. In those patients, post therapy minimal masking levels dropped indicating less acoustic energy was need to mask their problem tinnitus, interpreted as reflecting central changes. Taken as a whole, these data support the value of frequency specific tinnitus therapy.

Tinnitus loudness matchings in relation to annoyance and grading of severity

Objective: To measure and compare different parameters of tinnitus loudness obtained via matching and to investigate their associations with self-reported severity of tinnitus. Methods: From the audiology department 18 patients with unilateral tinnitus of sensorineural origin were selected. They underwent pure-tone audiometry, and in a matching paradigm their tinnitus pitch was estimated. Loudness was assessed at tinnitus frequency and at the frequency of best hearing and both were expressed in sensation level (SL) and hearing level (HL). Moreover, minimal masking level (MML) with white noise was assessed as well as thresholds for the tinnitus tone and a comparison tone in the contralateral ear when tinnitus was masked. Results: Annoyance and grading of severity were associated with measures of loudness expressed in HL, MML, and pure-tone audiometry. Loudness in SL was not associated with self-reported severity. Tinnitus loudness, matched at the frequency of best hearing instead of the tinnitus frequency, appears to be less dependent on HL, while still being associated with distress and grading of severity. Conclusion: Severity of tinnitus is related to hearing thresholds, and loudness in SL provides little clinically useful information.

Psychoacoustic Measures of Tinnitus

This report reviews research from the 1930s to the present that has extended our understanding by investigating the characteristics of tinnitus that can be studied using psychoacoustic techniques. Studies of tinnitus masking and residual inhibition began in the 1970s, leading to the therapeutic use of tinnitus masking and a consequent increase in research devoted to tinnitus measurement. In 1981, the CIBA Foundation symposium on tinnitus advocated general adoption of four tinnitus measures: (1) pitch, (2) loudness, (3) maskability, and (4) residual inhibition. Since then, psychoacoustic research into all four topics has proliferated, yielding many valuable insights and controversies concerning the details of measurement techniques. A consensus has emerged that neither the loudness nor other psychoacoustic measures of tinnitus bear a consistent relation to the severity or perceived loudness of tinnitus. Nevertheless, quantification is needed in clinical trials of proposed treatments and in a variety of other types of tinnitus research. Standardization of techniques for specifying the acoustic parameters of tinnitus thus continues to be an important research goal.

Estimating the contribution of non-sensory factors to infant-adult differences in behavioral thresholds

Estimates of behavioral thresholds of infants are elevated to those of adults. Explanation for the differences include auditory sensory factors and non-sensory factors, but no direct estimates of the relative contributions of these two factors have been made. In this investigation, thresholds in quiet and in increasing levels of a masking noise for a 1 kHz gtone, in infants 8 to 11 months old and in adults, were determined. The infant-adult difference in unmasked threshold was compared to the infant-adult difference in an estimate of the minimum masking level (MML) that was derived from the masking data. The intensity level of a masking noise at which masking begins is assumed to be independent of the non-sensory factors that impact on the threshold value itself. Therefore, it is reasoned that the infant-adult difference in MML reflects more closely differences in auditory sensory factors than does the infant-adult difference in unmasked threshold. In the region of 1 kHz, the infant-adult difference in behavioral threshold was 12 dB and the infant-adult difference in MML was 8 dB. Therefore, according to our assumptions, 8 dB of the infant-adult difference in unmasked threshold is accounted for by sensory factors and the remaining 4 dB must be attributable to non-sensory factors.

Neurophysiological model of tinnitus: Dependence of the minimal masking level on treatment outcome

Validity of the neurophysiological model of tinnitus (Jastreboff, 1990), outlined in this paper, was tested on data from multicenter trial of tinnitus masking (Hazell et al., 1985). Minimal masking level, intensity match of tinnitus, and the threshold of hearing have been evaluated on a total of 382 patients before and after 6 months of treatment with maskers, hearing aids, or combination devices. The data has been divided into categories depending on treatment outcome and type of approach used. Results of analysis revealed that: i) the psychoacoustical description of tinnitus does not possess a predictive value for the outcome of the treatment; ii) minimal masking level changed significantly depending on the treatment outcome, decreasing on average by 5.3 dB in patients reporting improvement, and increasing by 4.9 dB in those whose tinnitus remained the same or worsened; iii) 73.9% of patients reporting improvement had their minimal masking level decreased as compared with 50.5% for patients not showing improvement, which is at the level of random change; iv) the type of device used has no significant impact on the treatment outcome and minimal masking level change; v) intensity match and threshold of hearing did not exhibit any significant changes which can be related to treatment outcome. These results are fully consistent with the neurophysiological interpretation of mechanisms involved in the phenomenon of tinnitus and its alleviation.

The usefulness of nimodipine, an L-calcium channel antagonist, in the treatment of tinnitus.

Thirty-one patients were drawn from a tinnitus clinic, screened for other medical problems and treated for 4 weeks with 30 mg nimodipine four times daily. Before and after treatment, the intensity of their tinnitus was assessed subjectively on a scale 1-10. Five patients reported to have a great improvement in their tinnitus whilst two claimed a worsening of the condition. Of the five positive responders, four were treated further with 30 mg nimodipine per day for 4 weeks and 60 mg per day for a further 4 weeks. During this treatment they were assessed more objectively by the determination of the minimal masking level using narrow band noise. There was a good correlation between the subjective and objective assessment of their responses.

High-frequency audiometry. Masking in electric bone-conduction audiometry.

Recently, the 'electric bone-conduction' (EBC) audiometer (Audimax 500) has been used to measure high-frequency (HF) hearing. With this audiometer stimulation is binaural. No commercial masking method was available. In this study, white noise from a Madsen OB822 audiometer and presented via Sony MDR-V4 dynamic earphones, was used for masking. The masking and cross-hearing effect was measured in 8 unilaterally deaf subjects and the masking procedure was tested with 104 young normal-hearing subjects. The results showed that the EBC signals can be masked with air-conduction signals, and thus, the EBC measurements reflect monaural thresholds. The minimum masking level was 50-60 dB SPL in the HF range. There were no cross-hearing problems in the HF range with the earphones used. At the frequencies 0.5-14 kHz, the better ear's masked EBC thresholds were on the average 2.6 dB (range 0-4.5 dB) poorer, compared with the binaural EBC thresholds, indicating a binaural summation effect.