Donna L. Neff
Christina J. Kessler
Boys Town Natl. Res. Hosp., 555 N. 30th St., Omaha, NE 68131
Four listeners completed 2IFC sample-discrimination tasks for frequency (SDF), in which they judged which of two tones or tone pairs was drawn from the higher of two frequency distributions. The distributions were separated in mean frequency by 200 Hz (100-Hz s.d.). The main conditions examined SDF at 2100/2300 Hz, in isolation or with random-frequency tones (Gaussian distributed, 100 Hz s.d.), fixed-frequency tones, or noise bands (600-Hz wide) added on both sides of the SDF region, or a single random-frequency tone added on the high or low side. Stimuli were equated in total power. Frequency position of the extraneous stimuli relative to the SDF region was varied. Flanking random-frequency tones produced the largest decrements in performance, with most listeners showing little recovery even at maximum distance from the SDF region. A single random-frequency tone below the SDF region degraded performance more than one presented above. Flanking fixed-frequency tones also produced large performance decrements that were relatively independent of distance. Noise bands produced little interference unless they overlapped the SDF region. Thus SDF can be affected by distant extraneous tonal stimuli, particularly those sharing similar patterns of variation. [Work supported by NIDCD.]