Among the five sensory organs, i.e., the organ of sight, organ of hearing, organ of taste, organ of smell and organ of touch, the organ of hearing detects mechanical vibrations of the compressional waves in the air. Human beings perceive these vibrations as sound. The mechanics of the sensory cells in the organ of hearing, which detect the mechanical vibrations of air, is very mechanical. Our hearing is very sensitive, and this is realized by the collaboration between the inner hair cells and outer hair cells of the organ of Corti. In this review, referring to the research findings of various previous researchers, we shall first explain the structures of the inner hair cells and outer hair cells of the organ of Corti. Then, we shall explain the sound perception mechanism of the inner hair cells. Finally, we shall discuss how the inner hair cells interact with the outer hair cells in the organ of Corti.
We reviewed the language development by long-term observation of two sets twins in each of which only one twin had hearing impairment. We analyzed the developmental test results (the intelligence test, PVT and reading), the mean length of utterance (MLU), the record of the mother and the video. There were no significant differences in the results of the developmental tests, although there appeared to be a difference in the language concept formation and seeming for there to be a limitation in the volume of information. The results suggest the need for active intervention from the early stage seemed to be necessary in children with mild to moderate hearing loss.
Combined use of objective testing (such as DPOAEs and ABR) and behavioral testing is recommended for pediatric audiologic assessment, whereas in adults, the results of pure-tone audiometry are usually not verified by objective testing. However, there are some reports of adult cases in which disparities have been demonstrated between the results of subjective and objective auditory testing. In this study, we investigated 38 patients initially diagnosed as having idiopathic sudden sensorineural hearing loss (idiopathic SSNHL) and 18 patients diagnosed as having Ménière's disease by DPOAE for objective hearing assessment. In 4 of the patients (2 of SSNHL and 2 cases of sudden hearing loss because of Ménière's disease), substantial discrepancies were observed between the pure-tone audiogram and DPgram. These 4 cases were finally diagnosed as having psychogenic hearing loss. DPOAEs are easy to perform, and are valuable for early detection of psychogenic hearing loss. The possibility of psychogenic sudden hearing loss should be borne in mind in adult cases. The percentage of cases of psychogenic causes among patients with SSNHL might be underestimated.
A disk recording of voices of deaf children in the early Showa period under the title of “the results of the oral method in commemoration of the one-year anniversary of Osaka Deaf Oral School (created in 1927)”, was played back to analyze the formant frequencies of the speech of 9 deaf children and have 14 specialists perform auditory-perceptual voice evaluation. These 9 children had been educated by the oral method in the Taisho period, before the use of the auditory acuity method with hearing-aids. This record may be the oldest historical data of voices of the deaf, and may also have other historical value, in that Toru Kato has left data obtained from a residual hearing table carried out using audiometer 2A for the first time in Japan. The subjects had severe bilateral hearing impairments, which prevented them from acquiring adequate conversational skills. They were voices recorded after one-year training, but were still inferior in terms of differentiation of the formant frequencies (F1, F2) of the 5 vowel sounds. The above results revealed that a prototype efficacy of the oral method was developed in the early Showa and the Taisho period.
In this study, we discuss the relationship between the amount of experience of hearing environmental sounds and the clarity of the auditory imagery of environmental sounds in people with hearing impairment. A total of 10 people with hearing impairment participated in this study. They performed a task in which they needed to indicate whether the presented picture and presented sound fit each other by pressing a button. The reaction time for judging whether a picture and sound fit each other was measured from the time of presenting the sound until the button was pressed. The reaction time was shorter when the participants heard sounds that they had experienced hearing many times before. These results suggest that the judgment improved because the auditory imagery was clearly evoked by presentation of pictures corresponding to environmental sounds that the participants had heard many times before. Hence, it is very important to encourage people with hearing impairment to pay attention to environmental sounds in their daily lives to promote the development of auditory imagery. Further studies are needed to examine the features of environmental sounds for which people with hearing impairment can create auditory imagery easily, and also for developing effective ways to create auditory imagery of environmental sounds.