Because of the recent advance of micro-computer, many investigators began to use it. Personal-computers used individually are convenient, useful and cheap. Therefore, a personal-computer and audiometer online system and audiometric programs were produced. In this online system we use an audiometer (Rion AA-61B), a personal-computer system (NEC PC-8801 or PC-9801) and I/0 board (input-output board; Neolog PCN-1201 or PCN-1098). Audiometric programs are written in BASIC, and we produced the following three programs. 1. Audiogram storage program. 2. Auto-audiometry program. 3. Békésy audiometry program.
Seven male infants showed wave I only or waves I and II on auditory brain stem response, congenital horizontal pendular nystagmus and hypotonia of the head and limbs in the early infantile period, and later developed paresis. The age of these patients ranged from three months to six years at the first examination, and they could attain neither head control, sitting, nor walking. The follow-up study of auditory brain stem responses revealed neither improvement nor deterioration of wave configuration. These infants responded well to voices and other sounds. The congenital nystagmus of frequency of 2-3Hz in each case was demonstrated by electronystagmography. The correlation between clinical signs and ABR was uncertain. However, these findings strongly indicated the nonprogressive inborn abnormalities in the lower brain stem. Patients with these characteristics have never been reported in the literature.
The intelligibility difference between the 57-S List and the 57 List was studied using six intensity levels in 12 cases of moderate and moderately severe sensorineural hearing loss. The results were summarized as follows: (1) The maximum discrimination score showed no significant difference between the two lists. The intensity level of the maximum discrimination score was obtained at the condition of 30dB on both lists. (2) Intelligibility on the two lists improved about 40 percent when the intensity level increased from 0dB to 30dB. (3) The 57-S List showed about 10 percent better results than the 57 List under the conditions of lower intensity level compared with that of the maximum discrimination score. (4) In the discrimination score of consonants on the 57-S List, voiceless consonants were improved under the condition of 30dB and 20dB. Voiceless consonants, voiced consonants and semivowels were identified under the 10dB condition. As for nasal and vowels, there were no significant differences between the 57 List and 57S List. Therefore, the 57-S List is considered to be available instead of the 57 List as far as the items (3) and (4) mentioned above are concerned.
This study was designed to compare the usefulness of hearing aids between behind-the-ear type and box type in hearing impaired children, as regards to the hearing threshold with hearing aid and it using situation in every day life. Thirty-seven hearing impaired children were investigated in this study. It was clarified that many children showed lower hearing threshold with behind-the-ear type hearing aid than those with box type hearing aid, and also that reducing behavioral difficulties, minimizing psychological annoyance and increasing motivation to use hearing were noticed in the cases of behind-the-ear type hearing aid.
The speech intelligibility of 36 hearing-impaired children who fitted hearing aids in early childhood was studied in relation to their hearing levels. The materials used to measure intelligibility were 100 Japanese syllables. The results were summarized as follows; (1) The speech intelligibility of hearing-impaired children depended strongly on hearing levels. The speech intelligibility of jo-ons (contracted sounds) was affected most seriously by hearing levels. (2) The articulation errors of vowels were numerous in cases of 100dB HL or over. (3) In relation to consonants, the articulation errors of nasals, flappeds and plusives were numerous in cases of 100dB HL or over, and those of fricatives were in cases of 80dB HL or over. The articulation errors of affricates were numerous even in cases of 79dB HL or below.
The scalp distribution of auditory brain stem potentials was recorded in cats. ABRs to binaural and monoaural click stimuli were recorded from 12 electrodes on the scalp in 29 cats. The highest voltage areas (HVA) in isovoltage topographic maps of ABR components (I, III and IV wave) were investigated. The HVA of I wave were concentrated on the occipital area in binaural series. In case of monoaural slimuli, these were deviated on the contralateral occipital area. The HVA of III and IV waves were distributed on the temporal area.
Audiological tests were performed for sixteen patients with brain stem disorders in order to study their impairment of auditory perception. Their brainstem disorders were caused by tumor, hemorrhage, encephalitis and degenerative diseases, and all of their auditory brainstem responses were abnormal. ABR abnormality was defined by absent ABR or disappearance of later waves or prolongation of wave V-I peak interval. The following audiological tests were performed: 1) Pure tone audiometry, 2) Speech audiometry, 3) Discrimination test of meaningless 53 monosyllables, 4) Minimal-pair identification test 5) Long vs short vowels identification test, 6) Accent identification test, 7) Prosody identification test and 8) Token test. The results were as follows: 1) Pure tone thresholds were within normal range in 12 of 16 patients. The remaining four patients showed a mild hearing loss. 2) Speech audiometry showed normal scores in all patients except for two cases with absent ABR. 3) However, the discrimination test revealed lower correct percent in most patients except for cases with prolongation of wave V-I in less than 3 standard deviations. 4) Other tests demonstrated no abnormalities in most patients except for two cases with absent ABR as well as the token test. Our results indicated that only discrimination test of meaningless 53 monosyllables could detect audiological abnormalities in patients with lesions of auditory pathway in brainstem. And this suggested that the patients were hard to perceive meaningless monosyllables with low redundancy but could hear very accurately other test stimuli with high redundancy.
Thirteen electrodes were implanted chronically at the epidural space of a guinea pig, and the scalp distribution of three kinds of auditory evoked potentials were examined in the unanesthetized animal: the positive slow waves of ABR, MLRs, and the potentials corresponded to the human 40Hz event related potentials (auditory ERP). The following results were obtained. 1. The positive slow waves of ABR were satisfactorily recorded from the midline of the occipital site, and they were recorded in the higher amplitude from the contralateral side to the stimulated ear than the ipsilateral one. 2. The MLRs were best recorded from the temporal site contralateral to the stimulated ear. The polarity reversal of MLRs was observed between the temporal site and the midline. 3. The auditory ERPs were most successfully recorded from the contralateral temporal site to the stimulated ear. The difference of the scalp distribution of the auditory ERPs between human and guinea pig was thought to be due to the difference of the scalp distribution of the positive slow waves of ABR and the MLRs.
Frequency distribution of two-tone suppression was measured in forward masking and a comparison of psychophysical and physiological results were examined. In each experiment, the masked threshold of 15ms probe tone caused by the addition of a 600ms second masker (M2) to a 600ms first masker (M1) was determined as a function of probe frequency. M1 was a narrow-band noise centered at 3kHz (F1) with 200Hz bandwidth. M2 was a narrow-band noise centered at 2.1kHz (F2) with 200Hz bandwidth. M1 and M2 were generated by band-pass filter with a slope of 215dB/oct. Probe tones were filtered by 192dB/oct band-pass filter with a bandwidth of two thirds of each critical band. The spectrum levels (N0) of maskers varied from-10 to 50dB SPL by 5 or 10dB steps. There was no silent interval between the maskers and probe tones in forward masking. The results were as follows: 1) In all cases, suppression was maximum near or at F1. This was true regardless of levels of F1 and F2. This implied that suppression magnitude was not related to the frequency difference between travelling wave peaks for F1 and F2 on the basilar membrane. 2) The effect of level on suppression was nonlinear, i.e., suppression magnitude was seen to be a monotonically increasing function, suppression magnitude, however, decreased for M1 or M2 level higher than N0 40dB SPL. This implied that within the auditory-nerve fiber's dynamic range, suppression behavior is related to AGC mechanism. 3) Suppression in a small amount occurred for lower frequency suppressor M2, but large suppression magnitude occurred for higher frequency masker M1, even though the suppressor M2 intensity was weak in values of 10-30dB. This indicated that suppression was generated as a result of interaction and implied that suppression played some role in the encoding of steady-state vowels and of sharp frequency discrimination at auditory peripheral level. These results agree with previously published reports on physiological suppression behavior and implied that suppression was generated as a result of bidirectional transduction that ocurred within hair cells and stereocilliary-tectorial structures, and that nonlinear transduction of suppression was attributed to the synapse mechanism.
It is known that hearing threshold of multi-handicaped children is difficult to determine by tests which require children's cooperation. The purpose of this study was to find out how to measure hearing threshold of multi-handicapped children. The subjects were 41 children aged from 2 years and 4 months to 11 years and 10 months. All of them were mentally retarded, accompanying with one or more of the following handicaps: visual, auditory, emotional and physical handicaps. Their mental level was not determined by standard intelligence tests. Conditioned orientation reflex audiometry was administered by an audiologist who was excellent to perform audiometry over a period of 5 years at intervals of 4 to 6 months. The results showed that: (1) COR audiometry was an effective test for measuring hearing thresholds of multi-handicapped children; (2) thresholds found at the first test tended to be higher than those at later tests, and that the lower thresholds at the second tests were mostly maintained in the following tests; (3) the criterion to determine hearing fluctuation was derived for frequencies 250, 500, 1000, 2000, and 4000Hz.
The acoustic otoscope designed by David W. Teele for accurate detection of middle ear effusion was used for various middle ear diseases. 1) Acoustic otoscopy is used for rapid screening and not affected by crying of a patient and cerumen in the external ear canal. Air seal in the ear canal is not necessary. 2) This device is based on the priciple that a sound wave in a tube is exactly cancelled by its reflection at a distance equal to 1/4 wavelength from the closed end of the tube. 3) The accuracy of this device was confirmed in a plastic model and a human temporal bone specimen. In these experiments, the reflectivity increased as the level of the fluid in the middle ear increased. 4) The results of clinical application in many children and adults indicated that the acoustic otoscope is useful for accuratedetection of otitis media with effusion.
Field hearing threshold of the subjects aided with a hearing aid was measured by automatically interrupted test tones at a distance of one meter from a speaker in a sound proof room. The dB dial of a sound generator was calibrated at a distance of one meter from the speaker in 5dB step in reference to 0.0002dynes/cm in a range of 0dB to 100dB. The frequency range of the test tones was limited to a range of 250 to 3000Hz containing the important frequencies for speech intelligibility. The aided thresholds reached to the fitting levels by controlling the volume and the frequency characteristic of the hearing aid. The fitting levels were 50dB at 500Hz, 45dB at 1000Hz, 30dB at 2000Hz and 25dB at 3000Hz, respectively. These were 20dB lower than the average speech spectrum of Piece and David. The highest score of intelligibility was obtained when the aided thresholds reached to the fitting levels. The clinical results were classified into 3 types and discussed. A theory of fitting hearing aid was presented as to what characteristic of hearing aid could fit the field hearing levels of the subjects without a hearing aid.