To improve the quality of life of patients with sensorineural hearing loss has remained a long-term challenge for medical researchers and physicians in the field of otology and audiology. Development of effective and fundamental therapies for this disease involves multiple processes, including analysis of the principles of operation of the cochlea of the inner ear using live animal models, and elucidation of the pathophysiological mechanisms of hearing loss. In this context, the study of the inner ear has been hampered by a number of hurdles-the cochlea is composed of tubular and delicate structures encased in a bony wall and the physiological signals elicited from this organ are too small and subtle to be detected by conventional methods. Accordingly, through interdisciplinary collaborations, my group has developed a few advanced analytical technologies and instruments, as well as created a computational model. In addition, my colleagues and I have conducted intensive analyses of live animals in order to clarify the mechanisms underlying “real” biological phenomena. In this review, I shall not only summarize the results of physiological analyses of the cochlear sensory epithelium and stria vascularis, but also describe an original microsensing system for real-time measurements of the pharmacokinetics in the live cochlea.

　We created a software that runs on a tablet computer that can evaluate auditory processing tasks, and implemented tested it in 16 adults and 33 children of the third grade of elementary school and above. Of these, the results of 15 adults and 29 children were analyzed to determine the correct answer rate, standard deviation, and reference value limits. Our analysis identified one child with difficulties in the binaural separation listening task and the figure & ground task. On the other hand, the task difficulty level was probably too high to examine the single syllable task with department store noise (-15dB SNR) in the adult group. The results also suggested that we should consider modifying the answer and/or inspection method or deleting of 2 tasks; the GAP counting task and the duration discrimination task of sustained sound.

　 We investigated the clinical background and current status of 16 children with multiple disabilities who had worn hearing aids for more than one year. The most common reason for consultation was newborn hearing screening (NHS) referral, and the NHS referral cases were significantly younger at the time of the initial consultation than the other cases. NHS referral was linked to early diagnosis and treatment of hearing loss in children with multiple disabilities. In terms of the underlying medical conditions, genetic disorders were the most common (10 cases, 63%). There was no relationship between the number of disabilities and the degree of hearing loss. Patients with epilepsy were significantly less likely to benefit from hearing aids. It took time to stabilize the hearing aids in patients who began wearing them later. However, even patients in whom it took a long time to stabilize the hearing aids were able to continue wearing them for a long time afterwards. For children with multiple disabilities, it may take longer to ensure that the device can be worn stably and the effect may be limited, but it is important to respond to individual needs according to the disability and pattern of development.

　 We report our experience of the use of cartilage conduction hearing aids in 12 cases. Bone conduction hearing aid wearers did not wish to use cartilage conduction hearing aids, because of lack of the sound volume. It was considered to be a good adaptation when aesthetics and wearing feeling were emphasized. For cases of bilateral chronic otorrhea, it was considered necessary to provide information, so that it would be an option when replacing hearing aids. In cases of single-sided deafness, it is easy to feel the effect of wearing hearing aid, regardless of whether or not the ear canal was closed. As they get older, they have fewer opportunities to visit medical institutions, but encounter more situations that require binaural hearing. It is necessary to obtain information on hearing compensation and opportunities for auditioning. In addition to the beneficial effects in cases of external auditory canal closure and chronic otorrhea, we found good efficacy also in severe single-sided deafness, and it was considered that the indication sould be broad.

　We investigated the QOL of elderly hearing-impaired people using three questionnaires used to evaluate the comprehensive health-related quality of life, subjective well-being, and social activity. The subjects were 149 people aged 65 years or older with moderate hearing loss who visited the Department of Otorhinolaryngology, Kitasato University Hospital, from October 2019 to December 2020. We surveyed the subjects using a questionnaire consisting of “basic questions,” “Subjective Well-Being Inventory (SUBI),” “lively social activity checklist (social activity),” and “SF-36ver2.” Comparison of the mean score on the SF-36 with the national standard value revealed a significant decrease only for the Mental Component Summary (MCS) in subjects in their 70s (p<0.025). A positive correlation was found between the scores on the MCS and SUBI, and a positive correlation was also found between social activity and the scores on the MCS and SUBI. Multiple regression analysis showed improvement of the score on the MCS as the average pure-tone hearing level deteriorated (p<0.05). Use of a hearing aid also tended to affect the decline in the score on the MCS (p=0.072).

　The acoustic stimulus for VEMP is a loud sound, and the safety limits of sound pressure to prevent acoustic trauma are still under investigation. Earphones for VEMP are often not calibrated periodically, and there is a risk of acoustic trauma if the sound pressure exceeds the reference level. The design of YE-103J insertion-type earphones attached to evoked potential measuring devices manufactured by Nihon Kohden Kogyo Co., Ltd., is different from that of earphones used? for audiometry, and their acoustic characteristics are unknown. Therefore, we evaluated the acoustic characteristics, including the frequency response, of YE-103J, and considered the safe sound pressure in VEMP based on previous studies on the auditory threshold shift to acoustic stimuli. YE-103J shows a larger dip of frequency responses than the insertion-type earphones used for audiometry, especially at 500Hz, so that it is necessary to lower the values set according to the actual measured sound pressure level, at least when using it at 500Hz. Based on previous literature, the safe sound pressure level was determined to be lower than 125dB SPL. VEMP should be performed in consideration of the efficacy and safety, especially with attention paid to the risk of acoustic trauma.

　Although studies have shown that Japanese monosyllables can be indiscernible to individuals with sensorineural hearing loss, the acoustic features that make these monosyllables difficult to discern have not yet been clearly identified. In this study, focusing on the initial acoustic energy, the relationship between the initial rise of the sound exposure level (L_AE [dB]) and the correct answer rate for monosyllables was examined. The L_AE is defined as accumulated sound energy level from the onset of the monosyllable. When the early arrival time (t_att) was defined by the duration required to reach a desired L_AE (L_att), the time on a logarithmic scale (logt_att) showed a strong negative correlation with the correct answer rate for monosyllables whose voice onset times were not less than 0ms. In other words, the correct answer rate was high for monosyllables whose L_AE value rose more steeply. The correlation became high for individuals whose speech intelligibilities were profoundly low (r=-0.77, p<0.01). Meanwhile, monosyllables whose voice onset times were less than zero had were associated with? vocal cord vibrations (VCV) in advance of the consonant parts, such that the equalized initial rises of the L_AE made the correlation obscure. The correct answer rates in elder people were decreased because of elimination of the VCVs, and it can thus be said that the initial acoustic energy including the VCVs affects speech discrimination.