Evoked otoacoustic emissions (EOE) were investigated bilaterally in 25 normal-hearing subjects. Three acoustic click stimuli, produced by one sinusoid of 1kHz, 2kHz or 4kHz were used. EOE were recorded from all ears, and their input-output functions were nonlinear. Among three click stimuli, EOE amplitudes were the highest in most ears by 1kHz click stimulus, but EOE thresholds did not differ significantly. EOE thresholds by 1kHz click stimulus existed between -25dBSL and 15dBSL, and their distribution had one peak at 0dBSL. The mean value of them was -2.2dBSL. Therefore, it was considered that the EOE thresholds of 1kHz click stimulus approximated the psychoacoustic thresholds of this stimulus. The interaural difference of EOE thresholds was small, and it was less than 10dB in 80.0% of total subjects. EOE thresholds had good reproducibility. From these results, it can be concluded that EOE can be useful for examining cochlear function and that the EOE threshold can be a significant parameter for EOE measurement.
The aim of this study is to investigate the clinical usefulness of stimulated oto-acoustic emission (OAE) recording in sensorineural hearing loss. The OAE was recorded by the double barreled acoustic probe which consisted of a subminor earphone and a subminiature microphone. The stimulus sounds were tone bursts (rise-fall time 1ms, total duration 3ms) with the frequency between 1kHz and 2kHz. The responses were averaged 256 times with the analysis time of 20ms. Based upon the analysis of OAE recording in 17 normal hearing subjects, the interaural difference of OAE pseudothreshold was found out as a most excellent clinical indicator. The reproducibility of various OAE parameters such as configuration of wave form, the resonance frequency, the pseudothreshold, the latency and the input-output function was also found to be excellent in repeated tests of 41 ears. The OAE was examined in various kinds of unilateral moderate and profound sensorineural hearing loss which included congenital deafness, mumps deafness, functional deafness and sudden deafness. The interaural difference of OAE pseudothreshold was more than 35dB in all cases of congenital deafness and mumps deafness which were considered as the inner ear deafness. In contrast with this, the interaural difference of OAE pseudothreshold was nil in all cases of functional deafness. Furthermore in sudden deafness, the positive correlation existed between the interaural difference of psychoacoustic threshold and that of OAE pseudothreshold and also the interaural difference of OAE pseudothreshold became smaller along with the recovery of psychoacoustic threshold. From these results, we concluded that the OAE could be usful as an excellent clinical tool to investigate the inner ear function.
The purpose of this study is to investigate the clinical usefulness of stimulated oto-acoustic emission (OAE) in the diangosis of functional deafness in children. The subjects were 10 patients of functional deafness under 14 years old including 3 unilateral hearing loss and 7 bilateral loss. All ears showed a sensorineural hearing loss with the range of 35dB to 79dB in pure tone audiogram. However, the thresholds of ABR and stapedial reflex were within normal range in all ears. Type V of Jerger's tracings in Békésy audiometry was found in 13 ears out of 16. The interaural difference of OAE pseudothreshold was nil even in all cases of unilateral functional deafness. There was no statistically significant difference of OAE pseudothreshold between in functional deafness and in normal hearing ears. In contrast with this, there was statistically significant difference of OAE pseudothreshold between in a functional deafness and in a profound sensorineural hearing loss such as inner ear anomaly and mumps deafness which were considered as the inner ear deafness. The results of this study support the hypothesis that the OAE could be the reflection from cochlear micromechanics of the inner ear and therefore the OAE recording could be the useful tool in the diagnosis of functional deafness of chidren.
Spontaneous otoacoustic emissions (SOAE) were recorded from normal hearing subjects using a sensitive microphone in the external ear canal. SOAE were recorded in 33% of 45 subjects, 24% of 90 ears tested. SOAE showed a higher incidence in female than in male. Its frequency was within 3000Hz. Patients with tinnitus also showed a tendency for a higher incidence of the presence of SOAE, but their SOAE frequency differed from that obtained from pitch-match technique. In our study, it seemed that there was few interrelations between SOAE and tinnitus. External puretone suppressed SOAE with nonlinear input-output function. We discovered that in the range of steep slope of input-output function a combination tone appeared with SOAE and a suppressor tone. Our observation indicated that there was an active nonlinear process in the cochlea.
Guinea pigs were anesthetized with urethane (1.2g/kg i.p.), and an alternating current at a frequency of Fc was fed into the scala media at the 2nd turn of the cochlea through a glass micropipet or plutinum microelectrode, and a pure tone at a frequency of Ft (Ft>Fc) was delivered to the ear canal with a hermetically attached earphone. The sound in the ear canal was picked up with a probe tube microphone. The frequency power spectrum analysis of the sound showed components at Ft±Fc in addition to Fc and Ft, as if the oscillation of Ft interacted with the Fc vibration in the cochlea, so as to be amplitude-modulated. The powers of the sidebands at Ft±Fc were decayed reversibly by frocemide (20mg i.a.) and the sidebands were disappeared irreversibly after loud noise exposure. Cardiac arrest suppressed genaration of the sidebands immediately, and their magnitudes became below the noise floor after 60-90min. The amplitude-modulation could not be deteted in kanamycin-treated (400mg/kg/day i.m. for 14days) animals.
1) We investigated the dependence of the 2f1-f2 level on the stimulus level with primary-tone levels equal. Our results showed that 2f1-f2 level grew with a slope near 1 when both primary-tone levels increase. Many investigators have pointed out that the observed slope is near 1 in the psychoacoustical examination. This result seems to be explained by the overlap of the excitation patterns of f1 & f2, assuming the saturating mechanics in vibration amplitude of the basilar membrane. 2. It is considered that the combination tone 2f1-f2 is generated by the nonlinear motion of the basilar membrane, and can indicate the inner-ear function. But it must be proved that the measurement system does not generate the 2f1-f2 tone in this investigation.
We study the distortion products evoked by twotone stimuli, ie combination tone which is obvious physiologically and psycho-acoustically, by analyzing the frequency spectrum in the ear canal sound pressure. We must consider those as follows; 1. Selection of proper apparatus, that is, low distortion oscillator, mixer, speaker, receiver, microphone and so on. 2. Proper sound pressure level of given twotones. Although we could actually detected combination tone in the ear canal sound pressure by our designed system, it is not yet for sure that non-linear distortion generated in the experimental apparatus could be completely eliminated In the future, at first we must rule out the non-linearity in the apparatus through a study in the dummy ears that have normal function of the external and middle ear but no function of the inner ear, and then it should be possible to evaluate the results of different kinds of ear diseases.
A great deal of time and effort have been spent in devising methods of storage and retrieval of audiometric data. For on-line storage and retrieval of audiometric data, we developed a new computerized data processing system. This system can record and display the results of five different audiometric tests including pure tone audiometry, Bekesy audiometry, impedance audiometry, speech audiomerty and ERA. Testing equipments for them can be attached directly to the computer. Speech audiometry is keyed in separately. The special merits of this system are as follows; (1) A large number of audiometric data from five kinds of test can be stored in this system. (2) This system has mainly two functions of data retrieval, that are to describe a patient's past data of audiometric tests and to reproduce one pure tone audiogram on several different audiograms. (3) This system can be operated on the basis of on-line real time processing. (4) Feeding audiometric data to the computer and data retrieval can be carried out simultaneously.
Pneumatization of the human middle ear and mastoid air cell system were studied to investigate whether or not volume increased after insertion of tympanostomy tubes. The volume was measured by direct method in 36 ears with otitis media with effusion for a period of one year. The volume increased significantly for three months (P<0.01). The volume showed no significant changes there-after at 6 and 12 months after insertion of tympanostomy tubes. The finding suggest that development of the mastoid air cell system was not affected by tympanostomy tubes.