刺戟時ラウドネス順応の基本的性質

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Basic principles of the measurement of adaptation were studied from following three points of view; the time course, relation between adaptation and the length of the duration of comparison tones and the adaptation for the interrupted tones.By using the procedure which was introduced by the authors (Loudness balance between continuous and interrupted tones), the time course and theptation of the development of adaptation were measured. Test tones were 1000 cps pure tones with the intensity ranging from 10to 60 db (SL) and the comparison tones were interrupted tones with the same frequency. The comparison tone was interrupted with the repetition period of 2500ms, duty cycle of 70%o and the rise and fall decay time of 25ms. The intensity of the comparison tone was regulated by the subject withBekesy type attenuator. In the result, it was concluded that the development of adaptation was very rapid, but decelerative. In the initial stage of the stimulation, it was so rapid that it could not be recorded by the Bekesy attenuation with speed of 2db/sec. Though the time required to reach the asymptote varied depending upon the intensity of the test tone, it usually ranged trom 30 to 90 seconds.For the second purpose, comparion tones with the length of duration ranging from 10 to 45 seconds were used in the dichotic balance procedure.They were given in two different fashions of tracking and descending. Two conclusions were drawn from the results. First, the longer the duration of the comparison tone, the lesser the adaptation measured were. Second, the values of the measured adaptation were strongly dependent upon the manner of the comparison stimulation, namely, about 25 db difference was observed between the values obtained by tracking and descending fashion.The authors supposed that the main cause of this discrepancy was the shifted loudness function due to the adaptation.Another two different experiments were done for the third purpose. By using the different kind of interrupted tones as the comparison stimuli in the authors procedure, the influences of the duty cycle and the repetition period of the comparison stimulus upon the measured adaptation were studied, whereby no clear influence was observed.Second, the adaptation for the interrupted tone was measured by asymptotic balance procedure. Two test tones which were interupted in the following manner were adopted. (1) Repetition period of 2500 ms and the duty cycle of 70%. (2) Repetition period of 100ms and the duty cycle of 70%. In the results, no adaptation was observed.In conclusion, the authors stressed that the development of the perstimulatory adaptation was so rapid that the comparison stimulus with 10 seconds or more duration shold not be used in the adaptation measurement. If such a stimulus with long duration was adopted in the adaptation measurement as a comparison stimulus, the values obtained were strongly dependent upon the stimulation manner of the comparison ear. The authors recommended the use of the interrupted tone for the comparison stimulus, whereby no adaptation for the comparison ear would be expected.
社団法人日本耳鼻咽喉科学会の論文

刺戟時ラウドネス順応の基本的性質

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