| Budget Amount *help |
¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1988: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1987: ¥800,000 (Direct Cost: ¥800,000)
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| Research Abstract |
Auditory processings in dynamic perceptions caused by frequency modulated tones(FM tones) and amplitude modulated tones (AM tones) were investigated in terms of a notion whether FM processing and AM processing mechanisms are in common with each other or not. Carrier frequencies of tones below 1 kHz were used. For tones modulated simultaneously in both frequency and amplitude (mixed FM-AM tones), modulating patterns of which were periodic (sinusoidal) or aperiodic (linearly changed during short burst duration) ones, detection thresholds of target modulation (FM or AM) were measured with respective interfering modulation (AM or FM). The detection performances were influenced by interfering modulation when FM and AM had the identical modulation rate, but not when FM and AM had aperiodic modulation or different modulation rates between them. Experiments of discrimination between FM tones and AM tones were also conducted under the condition that their subjective modulation depths were the same. Subjects showed good discrimination performance below about 10 Hz of modulation frequency. Data of dissimilarity judgment among FM tones, AM tones and mixed FM-AM tones were collected. Then multi-dimensional analysis based on the data was done. For 3 Hz of modulation frequency, psychological dimensions corresponding to changing pitch and changing loudness were extracted respectively. For 20 Hz of modulation frequency, on the other hand, they were combined into a composite dimension corresponding to a subjective "changing" property. These results suggest that FM processing and AM processing are essentially independent, but dependent on each other when FM and AM have the identical modulation rate, probably higher than 10 Hz. It is thus supposed that channels selectively tuned to periodicity of FM and AM exist in auditory pathway.
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