This study was performed for investigation of the relationship between the preference of formant-emphasized speech and the degree of hearing loss of the listeners. A few types of the formant-emphasized speech sentence were produced by amplification of extracting formant frequency bands. These materials were presented and comfortable listening was tested on 20 normals and 85 hearing impaired listeners in 2 grouqs of experimental conditions; A) (1) an original speech, (2) 6 times amplified formant-emphasized speech, and (3) a formant-extracted speech with elimination of nonformant frequency bands; B) (4) an original speech with a white noise of 20dB of S/N ratio and (5) the formant-emphasized speech with a white noise of 20dB S/N ratio. The listeners were asked to select the most comfortable listening condition in each group. The results showed that, in the group A (noise-free condition), the original speech was most comfortable in all subjects, and in the group B (noise-added condition), the formant-emphasized speech was most comfortable in the cearing impaired with a hearing loss of 40dB or greater. These results indicated that formant-emphasized speech can be useful for the hearing impaired in noisy condition.
The relationship between hearing threshold of pure tone audiogram and the waves and latencies of auditory brainstem responses (ABRs) was investigate in 42 patients with a sensorineural hearing loss. The results were as follows; 1) Appearance rates of waves I, III and V: Appearance rates decreased as hearing threshold increased but wave V appeared approximately 100% until about 70dB of hearing level. 2) The latencies of waves I, III and V: The latencies of waves I and III did not prolong even when hearing threshold increased. Wave V showed a tendency to prolong with increase in hearing threshold more than 70dB at 2 and 4kHz.
Transtympanic electrocochleograms were recorded in 15 patients with a sensorineural hearing loss at the different electrode positions. We have found another polarities of SP at the different electrode positions in some patients. In order to evaluate AP and SP amplitude, SP/AP ratio and polarity of SP, we therefore have recorded at four different positions with needle electrodes. We have frequently observed dominant negative SP in electrocochleography for detecting endolymphatic hydrops in the patients with suspected Meniere's disease. However, Some investigators reported that positive SP was sometimes recorded in such cases. The purpose of this study is to clarify how the different SP polarities were recorded at the near round window niche and the other areas. The results obtained were as follows. 1) Maximum AP and SP amplitude were recorded at the routine positions which we used. 2) Positive SPs were frequently recorded at the near position of the round window niche. 3) In electrocochleographic responses recorded by using the high frequencies, the incidence of negative SP was shown at low percentage, on the other hand, the positive SP was more frequently recorded at the near round window niche. 4) -SP/AP ratio was stable at every position. 5) It would be suggested that positive SP is mainly generated from the round window or the scala tympani of the basal turn.
Auditory evoked responses (ABR, MLR, SVR) were studied in infants with hydrocephalus who underwent shunt operation. The subjects in this study were 28 infants aged 2 month to 8 years old. Abnormality of ABR was recognized in 5 cases of congenital severe hydrocephalus and one case of postmeningitic hydrocephalus. All cases of Chiari malformation type II showed normal ABR, although CT scan showed abnormality of brainstem. Abnormalities of MLR or SVR with normal ABR were observed in 37% of the cases. 61% of the cases revealed abnormality of MLR or SVR. The modalities of auditory evoked responses in infants with hydrocephalus lead us to the following two conclusions. First, these ABR findings suggested that the influence upon the auditory pathway at the level of brainstem was different between congenital severe hydrocephalus and Chiari malformation type II. Second, the central auditory pathway rostral to the brainstem seems to ho influenced in most cases of hydrocephalus.
Kyoto city has two elementary schools and one junior high school for hearing impaired children. They have about 70 children in every year. We have examined hearing ability and articulation of these children once a year, since 1985. In the present study, we showed the result of these examinations of articulation, and the statistical analysis of their hearing, speech intelligibility and hearing ability in these children. The results obtained were as follows: 1) The hearing levels of the subjects without and with a hearing aid were 93.7dBHL and 57.6dBHL respectively on the average. 2) The speech intelligibility of them was 37% on the average, which was influenced by the hearing level without hearing aid. 3) The hearing ability increased when they were instructed by showing picture cards. 4) Articulation of the children in special classes for hearing impaired are not established, and it can be changed with ease. 5) The children who attend mainstreamed kindergardens showed higher avarage in speech intelligibility than inexperienced children.
In this study, we investigated the reliability of the audiometry with CNV (contingent negative variation), because the reproducibility of CNV is considered as lower than that of the other evoked responses appearing in short latencies. The minimal hearing threshold was determined in the three normal subjects independently from each of three different parameters, i.e., (1) The mean amplitude of CNV (2) the subjective audiometry and (3) the measurement of the reaction time to the 2nd stimulation, and the following conclusions were obtained. CNV audiometry with 2dB steps was feasible and the minimal hearing thresholds obtained from the mean amplitude of CNV agreed to the difference of ±2dB with the other thresholds from two parameters. Also, for each of the three parameters, the thresholds obtained in the three consecutive trials showed the reproducibility within the range of ±2dB. Depending those resuluts, the reliability of CNV audiometry was comfirmed within the range of ±2dB. However it was difficult that the minimal hearing thresholds upon 2dB steps CNV audiometry were determined by the simple establishment of the standard potential for judgments of positive or negative of CNV appearances. Therefor it was proved important that the minimal threshold was determined by the consective changes of the CNV amplitudes accompanied with the change of sound pressures of the 1st stimulation.
Binaural interaction (BI) in human auditory 40Hz steady state responses (SSRs), ABR and MLR were measured in the waking state and during sleep of 20 adults with normal hearing. The SSRs were elicited with sinusoidally amplitude-modurated (SAM) tones at 500Hz or with tone-pips of 2-1-2 cycles at the same frequency. ABR and MLR were recorded with the same tone-pips at a stimulus interval of 115ms. Stimulus intensity was fixed at 45dBnHL. BI was represented numerically in the ratio in amplitudes of binaurally evoked responses to summed monaural responses for the right and left ears. The mean values of RI in the responses were significantly higher (p<0.01) during sleep than in the waking state. The result suggested that sleep acted as a suppressive factor to the BI in the responses. Among the responses, the BI-values became lower in the order, ABR (slow component), SAM-tone SSR, tone-pip SSR, MLR (Pa), both in the waking and sleep states. Significant difference was found during sleep between the BI-values in MLR and each of other 3 responses. However, the significant difference in the BI-values between MLR and tone-pip SSR disappeard in the waking state.
The purpose of this study was to investigate the effect of stimulus material on dichotic listening test. We presented consonant-vowel-consonant-vowel nonsense syllables both dichotically and monotically to ten normal right-handed adults. The results from this experiment suggested that dichotic ear performance was affected by the monaural identifiability of the stimuli. In another experiment, we performed dichotic listening test to twenty normal right-handed adults with consonant-vowel-consonant-vowel nonsense syllables (i.e. zahe/gomo/zuho/karo/shipa/sere) that had 100% discrimination score monotically. In this experiment, right ear advantage was observed, We throught that it was important to select the stimulus material considering the purpose of the test.
The auditory evoked brain-stem responses induced by a bone-conducted sound were recorded in subjects with normal hearing and in those with conductive hearing losses including congenital aural atresia, secretory otitis media, discontinuity of the ossicular chain and otosclerosis. In subjects with congenital aural atresia, secretory otitis media and otosclerosis, the wave I was clearly obtained by a bone-conducted sound delivered contralaterally as well as ipsilaterally, whereas the clear recording of wave I was limited to ipsilateral stimulation in case of the discontinued ossicular chain and the normal subjects. This contralaterally induced wave I disappeared after surgery for congenital aural atresia and secretory otitis media. The generation mechanism of this phenomenon was not fully explained by the current theory of the bone conduction mechanism, i.e. compression and inertia. Further studies on this phenomenon will contribute to further clarification of the machanisms in the bone conduction as well as the sound transmission of the middle ear.
Twenty normal hearing subjects (volunteers) were divided into 2 groups. Group A consisted of 10 ears ranging in age from 6 to 28-year-old. Group B consisted of 10 ears ranging in age from 35 to 52-year-old. Auditory nerve action potential (AP N1) and cochlear microphonics (CM) were measured using promontory recording technique in electrocochleography. The differences between these two groups were discussed. AP N1 output potential showed significant difference at all sound pressures. AP N1 latency showed significant difference below the stimulus sound pressure of 30dBnHL. CM output potential showed significant difference at 90dBnHL stimulus sound pressure in each frequency. These significant differences are considered due to disorders of the inner ear hair cells in the high frequency area, showing a higher mean hearing level in Group B, as the aging changes, and/or due to ossification of the otic capsule according to aging. CM at 1kHz showed the lowest detection threshold nearly same as hearing level of pure tone audiogram at 1kHz.