Discrimination and Identification of Modulation-Frequency Using Noise, Tone, and Tonal-Complex Carriers

摘要

A two-interval, two-alternative, forced-choice discrimination task (2I-2AFC) and an identification task were used to measure listeners' abilities to resolve modulation frequency, using three different types of carrier--noise, a 1-kHz tone, or a tonal complex. Identification performance was not simply related to 2I-2AFC discrimination performance. Identification of stimuli near the edges of the range was relatively good compared with listeners' abilities to discriminate these stimuli, a result which has been found for other stimuli (e.g., Berliner, Durlach, & Braida, 1977). In addition, certain midrange stimuli were identified relatively well, indicating the effects of central factors that enhance the encoding of these stimuli. Results for the 1-kHz and the tonal-complex carrier showed enhanced identification of modulation frequencies in the range 50-80 Hz. The results for the noise carrier, however, indicated enhanced resolution only for modulation frequencies less than 54 Hz. Possible explanations for these effects are discussed, and it is suggested that a more detailed examination of the role of the stimulus context would provide some answers. Keywords: Amplitude modulation, Modulation frequency, Identification, Discrimination, Auditory psychophysics. (JHD)