Discrimination of frequency transitions as a function of spectral and temporal psychoacoustic cues

The present study examined discrimination of short duration frequency glides (60 ms) analogous to the second formant transition of speech. An interdependence of rate of change, frequency excursion, and duration complicates the study of frequency transitions, and to determine how these psychoacoustic cues impact upon perceptual decisions stimuli in the current studies varied as a function of offset frequency and rate of change. Three continua of computer synthesized signals were used to determine just noticeable differences (jnds) for signals described by: a constant onset frequency with diverging offset frequencies; varying onset frequencies with a constant offset frequency; and varying offset frequencies with a constant rate of change. To attenuate frequency onset information, a 20 ms of octave-band noise was appended to the beginning of each signal. Results showed that discrimination improved as a function of the available psychoacoustic information: covarying transition rate and offset frequency yielded smaller jnds than varying either offset frequency or rate of change alone. Discrimination of transitions is not a simple function of frequency excursion or rate of change and integration of rate-related and spectral properties is speculatively important in perceptual decisions regarding complex signals such as speech.