Amplification rationale for hearing aids based on characteristics of the Japanese language.

OBJECTIVE: Hearing aid amplification rationales have typically been developed by using global averages of the long-term average speech spectrum (LTASS) from Western European languages. However, there are few reports on hearing-aid amplification based on acoustic-phonetic characteristics of the Japanese language. This study's objective is to investigate the LTASS for Japanese, and to compare a typical amplification rationale originally developed mainly for Western European languages with an amplification rationale specifically adjusted to the LTASS for Japanese. METHODS: LTASS for two speech materials provided by four Japanese talkers were analyzed using 1/3 octave bandwidth filters. The speech was recorded with different levels of vocal effort, yielding three LTASS for "soft", "moderate" and "loud" speech. From these results, a gain offset of the hearing-aid amplification for Japanese was obtained as compared to ANSI S3.5. Speech intelligibility for an amplification rationale for Western European languages and the newly-developed Japanese version was obtained for presentation levels of 50 dB SPL, 65 dB SPL and 80 dB SPL. Nineteen people with mild to moderate hearing loss participated in the speech intelligibility experiment. Scores in% correct were arcsine-transformed and subjected to repeated measures ANOVA with pairwise comparisons of significant main effects using Bonferroni adjustments for multiple comparisons. RESULTS: The LTASS for Japanese was slightly different from the values of previous reports. A comparison of LTASS values to ANSI S3.5 with values for Japanese showed that the Japanese amplification rationale for "moderate" speech levels required more gain in the low-frequency area, and less gain in the high-frequency area. There was no significant difference in the speech intelligibility level between the amplification characteristics of Western European languages and Japanese language at each presentation level. CONCLUSION: It was shown that for hearing-aid amplification for Japanese, adjustments based on LTASS differences for Western European Languages could be made. This preserved speech intelligibility at the same level as the original amplification rationale, suggesting that there was no need to consider differences in phonetics of Japanese to optimize speech understanding.

Sound Localization and Lateralization by Bilateral Bone Conduction Devices, Middle Ear Implants, and Cartilage Conduction Hearing Aids.

Sound localization in daily life is one of the important functions of binaural hearing. Bilateral bone conduction devices (BCDs), middle ear implants, and cartilage conduction hearing aids have been often applied for patients with conductive hearing loss (CHL) or mixed hearing loss, for example, resulting from bilateral microtia and aural atresia. In this review, factors affecting the accuracy of sound localization with bilateral BCDs, middle ear implants, and cartilage conduction hearing aids were classified into four categories: (1) types of device, (2) experimental conditions, (3) participants, and (4) pathways from the stimulus sound to both cochleae. Recent studies within the past 10 years on sound localization and lateralization by BCDs, middle ear implants, and cartilage conduction hearing aids were discussed. Most studies showed benefits for sound localization or lateralization with bilateral devices. However, the judgment accuracy was generally lower than that for normal hearing, and the localization errors tended to be larger than for normal hearing. Moreover, it should be noted that the degree of accuracy in sound localization by bilateral BCDs varied considerably among patients. Further research on sound localization is necessary to analyze the complicated mechanism of bone conduction, including suprathreshold air conduction with bilateral devices.

Guidelines for the evaluation of hearing aid fitting (2010).

OBJECTIVE: The methods to evaluate the efficacy of the adjusted hearing aid for a hearing-impaired person are fitting tests. The tests include those presently carried out for evaluating hearing aid fitting, and the methods of testing and evaluation have been published as "Guidelines for the evaluation of hearing aid fitting (2010)" by the Japan Audiological Society. METHODS: Guidelines for the following 8 test methods are presented. (1) Measurements of speech performance-intensity functions and speech recognition scores; (2) Assessment of hearing aid fitting from the aspect of tolerance of environmental noise; (3) Measurement of real-ear insertion gain (measurement of sound pressure levels at the eardrum); (4) Measurement of the hearing threshold level and the uncomfortable loudness level (UCL) in sound pressure level (SPL) with an inserted earphone; (5) Aided threshold test in a sound field (functional gain measurement); (6) Prediction of insertion gain and aided threshold from hearing aid characteristics and the pure tone audiogram; (7) Measurement of speech recognition in noise; (8) Assessment of hearing aid fitting using questionnaires. In the above tests, (1) and (2) are mandatory tests, and (3) to (8) are informative tests. RESULTS: By performing test combinations properly selected from the above 8 tests, the benefits of a hearing aid could be determined. CONCLUSION: The above test methods were useful and valuable in determining the efficacy of the adjusted hearing aid for a hearing-impaired person during clinical practice.

Unwanted sounds generated with test tone presentation can spoil extended high-frequency audiometry.

Unwanted sounds from a commercially available audiometer were evaluated in terms of their effects on extended high-frequency (EHF) audiometry. Although the manufacturer reported that the audiometer conformed to relevant International Electrotechnical Commission (IEC) standards, the audiograms obtained using the audiometer were erroneous because the subjects had responded falsely to noise generated with the test tone presentation before detecting the test tone. Analyses of acoustic and electric output signals revealed that the audiometer generated most of the unwanted sounds, not the earphones that were used. Based on the measurement results, clinical implications of the measurement results are discussed for conducting more reliable EHF audiometry.

Acute idiopathic sensorineural hearing impairment at frequency exceeding 8 kHz.

CONCLUSIONS: Acute idiopathic sensorineural hearing impairment at a frequency exceeding 8 kHz (high-frequency range) was recognized in patients suffering from acute tinnitus without hearing loss. The cases in this study may contribute to clarifying the pathogenesis of tinnitus without hearing loss and evaluating its response to steroid therapy. OBJECTIVES: The aim of this study was to demonstrate the existence of acute idiopathic sensorineural hearing impairment only in the high-frequency range and to investigate its relation to tinnitus without hearing loss. METHODS: Five patients aged 29 years or younger who consulted a hospital within a few days after the onset of unilateral tinnitus without hearing loss were studied. We conducted audiometry involving the high-frequency range on first medical examination and on improvement in tinnitus, and investigated the association between the hearing findings in the high-frequency range and a tinnitus prognosis. RESULTS: All five patients showed abnormalities in the threshold in the high-frequency range on the affected side. In the three cases given prednisolone, tinnitus and the threshold abnormalities were reduced within 20 days. In contrast, tinnitus and the threshold abnormalities showed little change in two patients who were not treated.

Chronological changes in the eighth cranial nerve compound action potential (CAP) in experimental endolymphatic hydrops: the effects of altering the polarity of click sounds.

CONCLUSION: Using a guinea pig model of experimental endolymphatic hydrops, click sounds of altered polarity showed different latencies and amplitudes in hydropic compared with normal cochleae. Latency changes appeared as early as 1 week after endolymphatic obstruction. This method can help diagnose endolymphatic hydrops. OBJECTIVE: The goal of the study was to develop an objective electrophysiological diagnosis of endolymphatic hydrops. MATERIALS AND METHODS: Endolymphatic hydrops were created surgically in guinea pigs. The latency and the amplitude of the eighth cranial nerve compound action potential (CAP) for click sounds of altered polarity were measured up to 8 weeks after the surgery. RESULTS: At early stages after surgery, the latency for condensation clicks became longer, and at later stages the latencies for both condensation and rarefaction became longer. The discrepancy in the latencies for rarefaction and condensation click sounds (rarefaction minus condensation) became larger by the first week after surgery, but no further discrepancy occurred thereafter. Compared with latency changes, amplitude changes in the CAP were rapid and progressive following surgery, suggesting ongoing damage to hair cells.

Evaluation method for hearing aid fitting under reverberation: comparison between monaural and binaural hearing aids.

Some hearing-impaired persons with hearing aids complain of listening difficulty under reverberation. No method, however, is currently available for hearing aid fitting that permits evaluation of hearing difficulty caused by reverberations. In this study, we produced speech materials with a reverberation time of 2.02 s that mimicked a reverberant environment (a classroom). Speech materials with reverberation times of 0 and 1.01 s were also made. Listening tests were performed with these materials in hearing-impaired subjects and normal-hearing subjects in a soundproof booth. Listening tests were also done in a classroom. Our results showed that speech material with a reverberation time of 2.02 s had a decreased listening-test score in hearing-impaired subjects with both monaural and binaural hearing aids. Similar results were obtained in a reverberant environment. Our findings suggest the validity of using speech materials with different reverberation times to predict the listening performance under reverberation of hearing-impaired persons with hearing aids.

Olfactory event-related potentials in normal subjects and patients with smell disorders.

We developed a device to record olfactory event-related potentials (OERP) from the human scalp. Methyl-cyclopentenolone was used as the odorant element. A total of 50 stimuli were delivered. Each stimulus lasted 0.5 sec and was delivered once every three inspirations. Normal OERPs were obtained with this device. The positive peak latencies were approximately 350 msec (P1) and 700 msec (P2), respectively. OERPs were also recorded in 40 patients with smell disorders. A positive response at about 300-400 msec was recorded in 7 patients (all females, 15-59 years old). The other 33 patients showed no response. The high potential area of this positive peak was located in the centro-occipital region of the scalp. The latency and the high potential area of this peak were similar to P1 recorded in normal subjects. The source of this peak was considered identical to that of P1. This may be a response to the trigeminal nerve during odor administration. P2 was not recorded in the patients with smell disorders. P2 may therefore be a response to the olfactory nerve.

Electroencephalographic changes during intravenous olfactory stimulation in humans.

The intravenous olfaction test with thiamin propyl disulfide (TPD) is a simple procedure widely used in Japan. An olfactory stimulus is provided by intravenous injection of TPD (2 ml) over the course of 20 sec. The subject smells n-propyl mercaptan (a decomposition product of TPD discharged from the blood into alveoli) in expired air after treatment. In this preliminary study we recorded electroencephalograms (EEGs) in normal subjects during three stages: 1) eyes-closed rest (prestimulus), 2) olfactory sensation after TPD injection, and 3) disappearance of sensation. In each of these stages, we calculated and compared EEG powers according to the band components of each electrode position. This study was designed a) to evaluate by frequency analysis EEG changes during olfactory sensation after TPD injection, and b) to identify the most significant changes in EEG power according to frequency band and electrode location. During the intravenous olfactory stimulation, alpha 2 and beta 2 waves were activated over the frontal and temporal regions. After disappearance of olfactory sensation, these waves decreased in the same regions. EEG powers returned to prestimulus levels.

[Magnetoencephalographic responses to odor and non-odor by fast Fourier transformation analysis in humans].

Magnetoencephalographic (MEG) responses to odor (amyl-acetate) and non-odor stimuli for 1 second were recorded in 9 healthy volunteers (right handed) with a dual 37-channel SQUID (Magnes, Bti Co.) and evaluated by fast Fourier transformation analysis, with the following results: 1. On MEG analysis, the spectral density increase in the left mid-central region at a frequency of 7 Hz was significantly greater in response to odor than in response to non-odor stimuli. This greater increase is apparently related to the presence of the odor perception mechanism in the orbital frontal area, a major center of the olfactory system. 2. Both increased and decreased spectral density areas at a frequency of 8 Hz were observed over the right hemisphere when no stimuli was compared with non-odor and no stimulus compared with odor. These changes may reflect a high level of vigilance caused by stimulation. 3. When no stimulus was compared with non-odor stimulation, a significant spectral density increase at a frequency of 11 Hz was noted. Similar trends were observed at frequencies of 11 and 12 Hz when no stimulus was compared with odor. These findings indicated increased attention in response to random presentation of odor and non-odor. 4. Significant differences at frequencies from 14 to 24 Hz were noted in the contralateral hemisphere when no stimulus was compared with odor stimuli. MEG spectral densities at 21 and 22 Hz were also noted in the contralateral hemisphere when no stimulus was compared with non-odor stimulus. These differences apparently arise from the response of the somato-sensory cortex to non-odor stimuli and amyl-acetate. Alternation of MEG spectral densities at frequencies from 14 to 17 Hz and 23 to 24 Hz in the left hemisphere was noted when no stimulus was compared with non-odor and no stimulus was compared with odor. These results appear to be related to "emotions" of pleasantness and unpleasantness evoked by non-odor and odor.