Many patients suffering from tinnitus report that the severity of their tinnitus changes depending on the acoustic environment. Tinnitus is more intrusive and bothersome in silent environments and less severe in sound-enriched environments, suggesting that therapeutic strategies using sound (sound therapy) may be effective for the relief of tinnitus. Sound therapy together with directive counseling has been developed as tinnitus retraining therapy (TRT), based on the neurophysiological model of tinnitus. Sound therapy for tinnitus is still under investigation in respect of its specific protocol and effectiveness, however, it has been reported to be effective in about 80% of the patients. In this manuscript, we review sound therapy for tinnitus as a component of TRT.

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The guidelines of the test for evaluating the necessity of fitting a hearing aid (2008) proposed by Japan Audiological society states that the method to calculate the gain is based on the frequency response curve. The purpose of this study was to compare the gain calculated from the frequency response curve with the functional gain. The subjects were fifty-two adults (23 males and 29 females) with hearing loss. We compared them at five frequency points (250, 500, 1000, 2000, and 4000Hz) according to the guidelines. At each frequency, the average values had a significant correlation between the two gains. No significant differences were found between the gains at the 250, 500 and 1000Hz. The differences at 2000 and 4000Hz were, however, statistically significant. The functional gain at 2000Hz was 7.6dB higher than the gain calculated from the frequency response curve. Considering the errors of audiometric tests, the method of calculating the gain based on the frequency response curve may be acceptable as an assessment tool for hearing aid fitting.

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The purpose of this study was to verify the validity of the conversion procedure for a hearing aid prescription based on deriving dB sound pressure level (SPL; 2cm³ SPL or ear canal SPL). The procedure used dBHL audiometric data obtained with insert earphones, adding the coupler-to-dial difference (CDD) and the real-ear-to-coupler difference (RECD) to convert the data to SPL. To evaluate the acoustic factors affecting the CDD and the RECD, the difference of the acoustic level between 2 insert earphones (3A and 5A) and between 2 types of 2cm³ couplers (HA-1 and HA-2) were measured. The RECD and the real-ear-to-dial difference (REDD) of the direct output level of the audiometer were measured in the real-ear worn 2 acoustically modified earmolds, with a FONIX FP-35 probe tube-microphone system. The predicted REDD (CDD+RECD) values were compared to the measured REDD to verify the converting procedure. The results showed that the 2 insert earphones were acoustically different within 5dB in the 200∼4000Hz range and over 10dB at around 6000Hz. The difference between the 2 couplers increased as frequencies rose above 1000Hz. The predicted REDD corresponded to the measured REDD within 250∼4000Hz in each earmold, the difference did not exceed 3dB. The results demonstrated the converting procedure was valid and reliable for dB transformation. The CDD measured for an individual audiometer and the RECD measured in the real-ear can be used for deriving the SPL.

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In this study, noises and environmental sounds were classified according to their auditory impression with a Semantic Differential method for the selection of noise in hearing-aid fitting. Thirty-eight kinds of noises and environmental sounds were used, with three intensity levels of 55dBA, 65dBA and 75dBA. The factor analysis of the auditory impression of the sounds, obtained from twelve normal-hearing persons, showed three main factors of powerfulness, sharpness and pleasantness in timbre. The score of the powerfulness factor increased with an increase in intensity level for almost all of the sounds. The scores of sharpness and pleasantness, however, did not change with stimulus intensity. We further carried out a cluster analysis of the noises and the environmental sounds based on these factor scores at the intensity of 65dBA. With this analysis, the noises and the environmental sounds that are generally used in hearing-aid fitting could be classified with regard to the auditory impression. The classification may be useful for hearing-aid fitting, because another environmental sound from the same cluster group can be substituted without having to use all environmental sounds mentioned in hearing-aid user complaints.

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In this study, acceptable and unacceptable levels of eight environmental sounds were obtained from ten persons with normal hearing while listening to speech. Their results showed a significant difference among the sounds. Reproducibility of the obtained levels was observed for four repeated measurements. Unacceptable levels for speech and uncomfortable loudness levels (UCLs) without speech were compared. The UCLs to the environmental sounds were about 20dB higher than the unacceptable levels for speech. The UCLs of three kinds of environmental sounds showed a significant difference among repeated measurements. These results suggest that unacceptable levels for speech and uncomfortable loudness levels (UCLs) without speech are different indicators of general listening comfort.

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A speech recognition test in noise is proposed in the guidelines for hearing aid fitting assessment (2008). The decrease in speech recognition in the presence of noise for hearing impaired subjects with and without a hearing aid, and the validity of this section of the guidelines were investigated. Sixteen subjects with hearing impairment participated in this study. A 57-type monosyllabic word list was used as the signal. It was presented at 65dB sound pressure level (SPL) and “dB max” which is the highest speech recognition score was obtained. Speech noise was used as the noise, and signal-noise ratio was +10dB. The decrease in the speech recognition score in the presence of noise was measured, and the influence of the hearing aid on the recognition score was investigated. The results showed that the speech recognition score decreased under noisy conditions both with and without hearing aids. The degree of the speech recognition score decrease showed interindividual differences. Even if a hearing aid might have been well fitted, the speech recognition score decreased by 12-22% in 8 subjects. At dB max, no difference was observed in the speech recognition score decrease between the conditions with and without a hearing aid. Further study is necessary for the influence of noise on speech recognition.

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The objective of this study was to investigate the changes in subjective evaluation of simulated environmental noise by adjusting the settings of digital hearing aids. This study involved 10 models (5 manufacturers) of hearing aids, and subjects with normal hearing aged 20-22 years. The results indicated that hearing aids with a directional microphone and fitted with a noise reduction system showed a higher speech discrimination score than the others without any noisy background. The subjective evaluations differed due to the variety of the environmental noise encountered. We considered that multiple sources of different sound should be required for the evaluation of environmental noise. The speech discrimination score was found to correlate with the score of the environmental noise evaluation. From the results, when evaluating the functions of a hearing aid, we demonstrated the use of both subjective and objective tests.

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The purpose of this study was to investigate the improvement of the speech recognition score (SRS) by amplification at the conversational level, and to compare it with the expected improvement estimated from aided and unaided audibility of the test sound. The monosyllabic SRSs of 589 cases measured at the level of 65dBSPL in a sound field with and without a hearing aid were analyzed. The expected improvement of the SRS was estimated under the assumption that the dependence of both aided and unaided SRS on the speech intelligibility indices (SIIs) of the test sound is the same.
The SRS showed maximum improvement in cases of moderate hearing loss, and the average improvement was 31.7% for the cases with a mean hearing threshold level of between 40 to 90dB. In a multiple regression analysis, the maximum correlation with the improvement of the SRS was observed for 3 independent variables: unaided SIIs, increase in SII by amplification, and the maximum articulation score (MAS) of the unaided ear. The average SRS improvement was the same as the average expected improvement in a group of 373 cases in which the aided MAS was not significantly lower than the unaided MAS. This means that, on average, the quality of the speech sound at the conversational level emanating from the hearing aid did not so deteriorate as to decrease the SRS as compared with that expected from the aided hearing threshold if the MAS did not deteriorate with the use of a hearing aid.

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A total of 578 patients with idiopathic sudden sensorineural hearing loss (ISSHL) treated between 1994 and 2009 at our hospital were investigated in regard to the treatment regimens, final hearing levels, and the effect on the outcomes between different treatment regimens. Among the treatment methods, the admission rates were 68, 89, and 95% in grades 2, 3 and 4, respectively. The rates of patients treated with hyperbaric oxygen (HBO) were 24, 35, and 63% in grades 2, 3, and 4, respectively.
In the final hearing levels, the peaks of distribution around 10∼20dB were shown in grade 2 and 3, whereas a normal distribution pattern with the peak at 60dB was evidenced in grade 4. There was a clear difference in the final hearing distribution between grade 2-3 and 4. A logistic regression analysis indicated the following results: 1) In grade 2, there was no significant effect on the final outcomes whether the treatment methods were applied in the outpatient or inpatient setting; 2) In the patients treated with grade 3 and 4 in the inpatient setting, there was no significant difference in the effect on the final hearing outcomes whether HBO was added or not.

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