Effect of attic obstruction on the middle ear sound transmission was measured simultaneously by two different methods in four fresh human cadaver temporal bones. In the visual method, the displacement of the manubrium tip of the malleus (umbo) to a constant sound pressure of 124dB SPL at the TM was measured before and after attic obstruction under microscope with stroboscope illumination combined with a video measuring system. In the acoustical method, the effective sound pressure (SP) which was transformed into the energy of vibration of the TM, was measured before and after obstruction of the attic. The effective SP was obtained from three parameters; the SPs in front and behind the TM, and the phase difference between them. The results by two methods were in good accordance and showed that the attic obstruction improved middle ear sound transmission by 7±2dB at 2.4-3kHz and worsened it by 6±2dB at 0.6-0.8kHz.
The characteristics of 131 tinnitus patients (perceptive deafness and non-deafness), including psychosomatic examination were examined. Otber symptomes than tinnitus were neck and shoulder stiffness (61.3%), sleep disturbance (51.2%) and stress (42.4%). In CMI test, 33 (29.7%) of 111 patients showed type III or type IV. 44 (44.4%) of 99 patients were positive to Shellong test. But these two test results were similar to those of normal subjects. In the depression test, 41 (39.0%) of 106 patients tested showed depressive condition. This test differed from those of normal subjects.
Frequency distribution of two-tone suppression was measured in forward masking and the comparison of the 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 and M2 were noises with 200Hz bandwidth. The spectrum levels (No, L1, L2) of maskers varied from -10dB to 50dB SPL by 10dB step. In each experiment, probe tones were filtered with a bandwidth of two thirds of each critical band. The results were as follows: Frequency distribution of two-tone suppression was not dependent on the levels of M1 or M2. However, amount of suppression was dependent of the difference in intensity between two maskers, L1, L2 or overall, respectively. Also, frequency distribution of suppression indicated that the frequency producing the most suppression usually shifts downward as the amount of suppression increases. There was a systematic increase in rates of suppression growth for suppressors as L1 or L2 increased and suppression were greatest in high-F2 and least in low-F2. Thus, suppression magnitudes were always dependent on only the intensity of M2. Suppression was observed at all F1 (0.7-3kHz) and was dependent on the phase of the masker components or the phase between the masker and the probe tones. Characteristics of suppression were not in conflict with the assumption that this effect is caused by the variable component suppressing the other masker component. Suppression of primary neurons indicated that suppression was generated as the results of interations occuring within hair cells, and stereocilliary-tectorial structures, however, implied that psychophysical suppression added inhibition of the cochlear nuclei to suppression primary neurons.
The current visual scoring procedure in the ABR audiometry was investigated using 3 experienced scorers. The sample traces for the test were obtained from 3 adult ABRs stored in tapes. In order to lower the signal to noise ratio of the traces, they were averaged by 20, 40, 80, 160 and 320 stimuli. In one case, 5, 10, 20, 40 and 80 stimuli were averaged. At the level where the responses were detected at about 50% of the traces, complete agreement in the judgment between 3 scorers was found in 60-70% of the traces, while test-retest agreement of each scorer ranged from 67 to 90%. The false positive judgment was found in 5-21% of the traces without stimulation. When duplicate traces were presented, however, the false positive judgment was decreased remarkably to 1.7-5%.
The effect of low-frequency cut-off and removing a peak at 1kHz on noise control was studied in relation to the fitting of hearing aids. Measurements of uncomfortable levels (UCLs) of three kinds of surrounding noises were performed under three different low frequency cut-off slopes with two types of frequency response (with or without a 1kHz damper). Twelve individuals with moderately severe sensorineural hearing loss were tested. The following conclusions were obtained: 1) low frequency cut-off slopes are useful in reducing noise; 2) 1kHz dampers are more useful for making frequency responses with a single peak at 2500Hz than for reducing noise.
A novel tone generator for automatic recording of electrocochleogram (ECochG) by means of digital electronics has been developed. One of several sets of digitized wave forms, stored in a read-only memory (ROM), is read out through a digital-analogue converter synchronizing with an external control signal. The frequency of the tone can be controlled by changing the read-out speed. The circuit design is optimized in terms of clinical use. An alternately phase reversed tone output enables automatic signal processing to record a compound action potential (AP) or a summating potential (SP). By alternately inverting/non-inverting of the bio-signal in accordance with the alternate phase reversal of the tone output, cochlear microphnics (CM) can be recorded automatically.
The evoked oto-acoustic emissions were recorded from 13 normally hearing subjects. Click tone and 500, 750, 1000, 1500, 2000, 3000Hz tone bursts were used as stimuli for oto-acoustic emissions. A probe was made by a polyethylene tube with subminor-earphone and subminute transducer. The input-output relationships between the emissions and the stimuli were studied. The frequencies of emissions were constant, while the frequencies of stimuli were changed in each person. The oto-acoustic emissions evoked by tone-bursts had the lowest threshold at burst frequencies close to the emission's frequencies of each person. Clinically, if seemed useful to obtaine the emission induced by click at first, before the suitable frequencies for each person were found.
Sequential recording of the auditory brain stem response (ABR), middle latency response (MLR) and slow vertex response (SVR) under logarithmic time scale were applied for the 17 cases of central lesions, in order to obtain more informations as for the localization of the lesions. The recording is vertex-ipsilateral mastoid to the acoustic stimuli, click with 80dB nHL or 100dB nHL. The averaging numbers are 500 times and analysis time is 500msec. Pass-band of the filter is 2-2000Hz and sampling clock is 100usec on A-D conversion. The results were as follows; The modality of MLR and SVR showed remarkable changes by the site of the lesions. 1) Temporal lobe lesions gave influence upon ABR and MLR very few, however, the N-P2 component of SVR was greatly affected. 2) Subcortical lesions showed little variation upon ABR, however, latency-prolongation of each component of MLR and SVR or dicrease of their amplitude were clearly identified. 3) Some of the upper brain stem lesions showed almost normal SVR. 4) As for the lower brain stem lesions or C-P angle lesions, MLR and SVR provided poor information. 5) Degenerative disorders of the brain (ex. multiple sclerosis) could fairly be diagnosed by comparing the sequential changes of ABR and MLR with normal SVR. Logarithmic time-scale recording can identify the sequential modality of AEP, and pathological influence upon the auditory pathway by some central lesions could lead us to speculate the site of the lesions.
The relationship between loudness (indicated by sensation level) and three kinds of masking level (indicated by sensation level) at the frequency of the pitch of tinnitus was studied in 343 tinnitus ears without hearing loss or associated with cochlear deafness whose pitch was identified by pure tones. The definition of three kinds of masking level was as follows; The first masking level (ML) was calculated as the difference between masking level by band noise (indicated by audiometer level) and pure tone hearing level at the frequency of the pitch of tinnitus. The second masking level (BNML) was calculated as the difference between masking level by band noise (indicated by audiometer level) and band noise hearing level at the frequency of the pitch of tinnitus. The third masking level (PTML) was calculated as the difference between masking level by pure tone (indicated by audiometer level) and pure tone hearing level at the frequency of the pitch of tinnitus. The following results were obtained; 1) The minus value was obtained in 18.7% of loudness, in 32.9% of ML, in 2.3% of BNML and in 5.3% of PTML, respectively. 2) The correlation coefficient between loudness and masking level was 0.55 in ML, 0.53 in BNML and 0.67 in PTML. 3) The regression line between loudness (x) and masking level (y) was calculated. It was y=0.98x-1.71 in ML, y=0.67x+7.61 in BNML and y=0.90x+7.19 in PTML, respectively. 4) The PTML could be most useful among three kinds of masking level indicated by sensation level as an indicator of the intensity of tinnitus whose pitch was identified by pure tones.
Although several investigators had studied the cause of the on-off reaction on the acoustical stapedial reflex in man, any conclusive result has not yet been achieved. When we applied short tone burst to the contra-lateral ear, in some cases we observed two phased reverse response which seemed to be originated from the same cause as the on-off reaction. We observed the change of the amplitude of the wave due to the increase of the stimulus sound duration, difference of the latencies between reverse and regular responses. Moreover, we measured the activity of the guinea pig's stapedial muscle through EMG, and found no biphased activity, which Baust et al. had reported. Considering these results, we regarded the difference of the I-S joint's movement, which occured due to difference of shape of the head of the stapes, as the cause of the on-off reaction among some normal human subjects.