短音の周波数弁別に及ぼす先行音の効果

抄録

Auditcry response for the unsteady sound has been mainly discussed by means of "masking". In this paper, the effects of leading tone (interference tone) on frequency discrimination of a brief tonal signal were investigated and the auditory response in the transient state was discussed. Changes in frequency discrimination were measured as a function of the signal duration, the frequency separation between the interference tone and signals, temporal delay between the two and the intensity of tonal signal. The results obtained as folllws:1)Frequency discrimination deteriorates as the test tone decreases to the level lower than 20 dBSL, provided that the frequency of leading tone is same as one of the test tones (see Fig. 2). This phenomenon can be interpreted as a rise of minimum audible level of test tone due to forward masking. 2) Frequency discrimination of test tone with the leading tone whose frequency is the same as the test tone is almost same as in the case without the leading tone (see Fig. 4). Frequency discrimination, however, becomes, worse in the presence of leading tone with slightly different frequency from the test tone, and when the frequency of the test tone is 1000Hz, the interference effect of the leading tone is maximum for the frequence difference of 50. Hz. But frequency discrimination is little affected by leading tone when the difference of frequency from test tone becomes over 100Hz. 3) When the frequency of leading tone is 950 Hz, frequency discrimination does not become better, even though the time interval between the leading tone and the test tone is increased (see Fig. 5). Furthermore, the forward masking experiments were performed under the same condition as in the previous experiments to explore the relation between the temporal masking and the frequency discrimination and mechanisms of interference.