Sample discrimination of frequency differences with distracters

This study examined the effect of the type and frequency range of remote frequency distracters on sample discrimination of frequency differences (SD-F). For baseline SD-F conditions, normal-hearing listeners judged frequency differences between pairs of target tones drawn from Gaussian frequency distributions near 2000 Hz. In experiment 1, the distracters were pairs of random-frequency tones, fixed-frequency tones, or noise bands, with one distracter above and one below the target region. Three frequency separations of targets and distracters were tested, none overlapping the target region. Effects of fixed-frequency or noise-band distracters were small compared to that of random-frequency distracters, which drove performance to near chance. In experiment 2, dominance of the low-frequency distracter was supported by the effects of changing distracter level, by presenting only the higher- or lower-frequency distracter, and by the pattern of weights derived from trial-by-trial responses. Performance recovered only when the lower-frequency distracter was attenuated 40-50 dB relative to the targets. In experiment 3, all stimulus distributions were shifted 2 octaves higher in frequency; the stronger influence of the distracter frequency below the target remained. The results demonstrate the importance of both stimulus variability and frequency relationships in the interaction of targets and distracters for SD-F.