Advanced Hearing Research Articles

Cochlear implants in children.

In recent years, notable progress has been made in the rehabilitation of children with mild to moderate-severe hearing impairment using new and advanced hearing aids. The major problem which remained was the lack of availability of treatment options for those with severe-to-profound sensorineural hearing loss who received little or no benefit from conventional amplification. The purpose of the cochlear implant is to provide these children with direct electrical stimulation of the auditory nerve. A hearing aid amplifies incoming stimuli while a cochlear implant attempts to replace a function lost by the cochlea. In a normal hearing ear, the hair cells within the cochlea act as a transducer of mechanical energy of sound vibration to energy capable of enervating the eighth nerve. The consequence of a decrease in the number of hair cells is the loss of ability of the cochlea to perform the functions, which result in eighth nerve stimulation. The implant replaces the task of the lost hair cells by converting mechanical energy into the electrical energy necessary to excite the remaining cochlear neurons. In order to truly appreciate the application and unfolding of cochlear implants as applied to the pediatric population, it is important to summarize the development of the devices in general.

Application of Advanced Hearing Instrument Systems with Children

The goal of amplification for a child with hearing loss is to deliver an audible signal which maximizes the possibilities of speech perception. Wireless transmission systems are the communication mode of today. Improved communication for infants, children, and teenagers is now available with today's programmable hearing aids which receive a direct input from a remote sound source using multi-microphone technology. The key is to fit the child with hearing loss with the appropriate amplification, and then to provide support systems, the integrated FM receiver (the link), and secondary microphone choices (third Ear) which enhance the choices of auditory signals.

Modeling of acoustics of hearing aid earmold systems

The earmold system of hearing aids guides an amplified and compressed sound into the ear canal. The description of the propagation of acoustical waves in this system is complex because of the fact that the auditory tube is not straight and the eardrum does not form a perfectly flat end. In more advanced hearing aids, the earmolds are acoustically fitted, according to the patient’s needs. However, this is done experimentally during the fitting process. Modeling of earmolds with irregular shapes can be based on the approach widely used in speech acoustic and in digital sound synthesis, namely the physical modeling of acoustical waveguides. The elaborated model uses fragments of tubes of different diameters and lengths. The difference in acoustic impedance at the boundaries of each two fragments is described by the reflection coefficient. The acoustic wave propagation is modeled using a pair of delays. The model enables the finding of a spectral response characteristic of a hearing aid earmold system in the process of its matching to the patients needs. The details of the proposed approach and some results will be presented in the paper. [Work supported by KBN, Poland, Grant No. 8 T 11E 03415.]

Significance of Head-shaking Nystagmus in the Evaluation of the Dizzy Patient

In a series of studies, the phenomenon of head-shaking nystagmus (HSN) was assessed in 50 control subjects and 1364 consecutive dizzy patients who underwent formal electronystagmography (ENG) at the Toronto Hospital Center for Advanced Hearing and Balance Testing. HSN was compared in a series of 30 patients who underwent conventional electro-oculography (EOG) vs magnetic (scleral) coil eye movement recordings. Clinical correlation of HSN to other parameters of the ENG test battery was performed in another sub-series of 300 patients with known diagnoses. HSN was identified in 31.7% of dizzy patients vs 24% of control subjects. No significant difference in its manifestation was noted between active vs passive head-shaking tests or on EOG vs magnetic (scleral) coil eye movement recordings. When compared to other aspects of the ENG test battery, HSN was neither specific nor sensitive for vestibular dysfunction. It nevertheless correlated well with the presence of a caloric reduction and with increasing R/L excitability differences on ENG testing. When present, HSN was characteristically monophasic in 76.8%, biphasic in 22.7% and triphasic in 0.5% of subjects. The initial direction of HSN generally obeyed Ewald's second law, but the reverse was noted in 27% with monophasic and 17.6% of patients with biphasic HSN. In the subseries of 300 patients with known diagnoses, the presence of HSN was statistically significant ( p <0.05) in patients with peripheral vestibular dysfunction vs psychogenic dizziness. Its presence was also significant in well-documented peripheral vestibular disorders such as Meniere's disease ( p <0.01), vestibular neuronitis ( p <0.05) and acoustic neuroma ( p <0.05). Localization of the disease involvement based on the initial direction of HSN was especially unpredictable in patients with Meniere's disease. The significance and usefulness of the head-shake test in the otoneurological evaluation of the dizzy patient is further commented on.

A programmable sound processor for advanced hearing aid research.

A portable sound processor has been developed to facilitate research on advanced hearing aids. Because it is based on a digital signal processing integrated circuit (Motorola DSP56001), it can readily be programmed to execute novel algorithms. Furthermore, the parameters of these algorithms can be adjusted quickly and easily to suit the specific hearing characteristics of users. In the processor, microphone signals are digitized to a precision of 12 bits at a sampling rate of approximately 12 kHz for input to the DSP device. Subsequently, processed samples are delivered to the earphone by a novel, fully-digital class-D driver. This driver provides the advantages of a conventional class-D amplifier (high maximum output, low power consumption, low distortion) without some of the disadvantages (such as the need for precise analog circuitry). In addition, a cochlear implant driver is provided so that the processor is suitable for hearing-impaired people who use an implant and an acoustic hearing aid together. To reduce the computational demands on the DSP device, and therefore the power consumption, a running spectral analysis of incoming signals is provided by a custom-designed switched-capacitor integrated circuit incorporating 20 bandpass filters. The complete processor is pocket-sized and powered by batteries. An example is described of its use in providing frequency-shaped amplification for aid users with severe hearing impairment. Speech perception tests confirmed that the processor performed significantly better than the subjects' own hearing aids, probably because the digital filter provided a frequency response generally closer to the optimum for each user than the simpler analog aids.

若年性一側性高度感音難聴の側頭骨画像所見

若年性一側性高度感音難聴の側頭骨画像所見

先天性高度感音難聴児に対する人工内耳埋め込み術後の行動学的変化と言語成績 （第二報）

先天性高度感音難聴児に対する人工内耳埋め込み術後の行動学的変化と言語成績 （第二報）

A preliminary report: clinical effects of otic solution of ofloxacin in infantile myringitis and chronic otitis media

Patients with infantile myringitis or chronic otitis media may refuse treatment when antibiotics are to be administered orally. The present study was undertaken to treat myringitis and chronic otitis media with an otic solution of non-ototoxic ofloxacin in 21 children aged 0–15 years. They consisted of eight normal children, four children operated on for microtia, and nine so-called handicapped children mainly with advanced hearing impairment and retardation in mental development, or eight children with myringitis and 13 children with chronic suppurative otitis media. Otic solution of ofloxacin was instilled into the ear twice daily, in the morning and evening, for 7 days or more, the treatment time being 10 min. With the causative pathogen completely eradicated in 14 patients and the bacterial count reduced in three patients and unchanged in two patients, the results of treatment with ofloxacin may be considered to be excellent.

4th Conference on Issues in Advanced Hearing Aid Research

First Page

先天性サイトメガロウイルス感染により高度難聴と平衡障害を呈した１例の発達について

先天性サイトメガロウイルス感染により高度難聴と平衡障害を呈した１例の発達について

高度難聴幼児への人工内耳の適応

高度難聴幼児への人工内耳の適応

Hearing aids: New (and improved) answers for your patients

Educational objectives: To answer patient questions about amplification with updated, accurate information and to understand new concepts in selection and fitting of technologically advanced hearing aids.

A portable programmable digital sound processor for cochlear implant research

A programmable sound processor which utilizes digital signal processing has been developed for hearing prosthesis research. It incorporates a Motorola DSP56001 integrated circuit, 32 K words of memory, a 12 b analog-to-digital converter, and a data formatter and transmitter which conveys control codes to the receiver-stimulator of a cochlear implant. The processor is pocket-sized and battery powered. It has been programmed to emulate the Spectral Maxima Sound Processor for the University of Melbourne/Nucleus 22 electrode implant, and is currently being used by several implantees. In continuing research, speech processing programs are being improved, and other applications, including signal processing for binaural implants and advanced hearing aids, are being developed. >

On the measurement of source separation

It has been conjectured that certain acoustic cues present in a complex waveform are used by the auditory system to decompose that waveform into a set of auditory sources. The disparity between the perceived source(s) and the physical sources in such phenomena as stereophony suggests that there is not necessarily a one-to-one correspondence between the acoustic composition of signals and the perceptual decomposition of the combined signal into auditory sources. In an earlier paper [Wakefield and Runkle, Issues in Advanced Hearing Aid Research Conference (May 1992)], a method was proposed for measuring the strength of such cues adaptively, however, the hypothesis that the measuring technique itself was responsible for the results could not be rejected. In the present paper, an alternative measuring tool is introduced that is capable of independently suppressing and enhancing different spectral regions, unlike the original tool. Results are presented concerning the salience of co-modulation, harmonicity, onset and offset cues, and amplitude spectrum with respect to auditory sources using the new tool. A recognition paradigm is integrated into the proposed method to help validate the results. [Work supported by grants from the NIH NIDCD and from Ford Motor Company.]

Peak-picking fundamental period estimation for hearing prostheses.

A real-time peak-picking fundamental period estimation device is described which is used in advanced hearing prostheses for the totally and profoundly deafened. The operation of the peak picker is compared with three well-established fundamental frequency estimation techniques: the electrolaryngograph, which is used as a "standard" hardware implementations of the cepstral technique, and the Gold/Rabiner parallel processing algorithm. These comparisons illustrate and highlight some of the important advantages and disadvantages that characterize the operation of these techniques. The special requirements of the hearing prostheses are discussed with respect to the operation of each device, and the choice of the peak picker is found to be felicitous in this application.

対側型遅発性内リンパ水腫の聴力変動について

We treated 42 patients with delayed endolymphatic hydrops (DEH) : 33 ipsilateral, 7 contralateral, and 2 bilateral. We conducted a clinical study of the 7 patients with contralateral DEH.Patients with contralateral DEH have a profound hearing loss in one ear, and eventually develop symptoms of endolymphatic hydrops in the opposite ear (only hearing ear) -fluctuating hearing loss with or without vertigo-, which is a very serious problem not only for the patient but also for otologist.The cause of the profound hearing loss in our 7 cases was head trauma, otitis media and mumps (1 case each), and juvenile unilateral deafness of unknown etiology in 4.The chief complaint was fluctuating and progressive hearing loss in the better hearing ear in 6, and rotatory vertigo caused by the normal hearing ear in 1.In the diagnosis of contralateral DEH, the clinical history is most important and the glycerol and furosemide tests are very useful.In the treatment of contralateral DEH diuretics and steroids have been employed. In those who failed to respond to conservative therapy, epidural shunt operation on the endolymphatic sac was performed in our clinic. The treatment was effective in many cases, but in some cases hearing loss progressed in spite of the intensive therapy. In the patients with advanced hearing loss already in the better hearing ear, it is very difficult to perform an operation because of the relatively high risk of making the hearing worse. We have tried γ-globulin therapy in some patients who showed a poor response to conventional therapy. This therapy sometimes yielded good results. The action of the γ-globulin on the inner ear and the endolymphatic sac is still unknown. But we believe that we should always strive to search for a more effective conservative therapy as well as trying to be more skillful in surgical management.