Detection of acoustic repetition for very long stochastic patterns

Guttman and Julesz (1963) employed recycling frozen noise segments (RFNs) a s model stimuli in their classic study of the lower limits for periodicity detection and short-term auditory memory. They reported that listeners can hear iteration of these stochastic signals effortlessly as "motorboating" f or repetition periods ranging from 50 to 250 msec and as "whooshing" from 2 50 msec to 1 sec. Both motor-boating and whooshing RFNs are global percepts encompassing the entire period, as are RFNs in the pitch range (repetition periods shorter than 50 msec). However, with continued listening to whoosh ing (but not motorboating) RFNs, individuals hear recurrent brief component s such as clanks and thumps that are characteristic of the particular wavef orm. Experiment 1 of the present study describes a cross-modal cuing proced ure that enables Listeners to store and then recognize the recurrence of po rtions of frozen noise waveforms that are repeated after intervals of 10 se c or more. Experiment 2 compares the relative saliencies of different spect ral regions in enabling Listeners to detect repetition of these long-period patterns. Special difficulty was encountered with the 6-kHz band of RFNs, possibly due to the lack of fine-structure phase locking at this frequency range. In addition, a similarity is noted between the organizational princi ples operating over particular durational ranges of stochastic patterns and the characteristics of traditional hierarchical units of speech having cor responding durations.