Biomedical subjects

Donna L Neff

Publications and source records attributed to Donna L Neff.

3 recordsLinked to original sources

PubMed2005

Effect of variability in level on forward masking and on increment detection.

In the first of four experiments, all with the same four subjects, varying the level of a forward masker from interval to interval in a two-interval forced-choice (2IFC) adaptive procedure had little effect on threshold. In the second experiment, the signal level was fixed and performance was measured in units of d'. Varying the level of the forward masker again had little effect. Analyses of trial-by-trial data indicated that subjects did not vote for the interval with the higher-level masker, as would an energy detector. Performance was better on trials where the masker level in the interval with the signal was lower and was relatively independent of masker level in the nonsignal interval. In the third experiment, these results were replicated for a wider range of masker variability and with maskers lower in frequency than the signal. In the fourth experiment, the same range of variability from interval to interval was imposed on the level of the pedestal in an increment-detection task. Results were similar to those observed in forward masking. The results suggest that decision processes involved in both forward masking and increment detection are similar and that neither is based on energy detection. Template matching remains a viable alternative.

Acoustic Stimulation↗

PubMed2004

Cuing effects for informational masking.

The detection of a tone added to a random-frequency, multitone masker can be very poor even when the maskers have little energy in the frequency region of the signal. This paper examines the effects of adding a pretrial cue to reduce uncertainty for the masker or the signal. The first two experiments examined the effect of cuing a fixed-frequency signal as the number of masker components and presentation methods were manipulated. Cue effectiveness varied across observers, but could reduce thresholds by as much as 20 dB. Procedural comparisons indicated observers benefited more from having two masker samples to compare, with or without a signal cue, than having a single interval with one masker sample and a signal cue. The third experiment used random-frequency signals and compared no-cue, signal-cue, and masker-cue conditions, and also systematically varied the time interval between cue offset and trial onset. Thresholds with a cued random-frequency signal remained higher than for a cued fixed-frequency signal. For time intervals between the cue and trial of 50 ms or longer, thresholds were approximately the same with a signal or a masker cue and lower than when there was no cue. Without a cue or with a masker cue, analyses of possible decision strategies suggested observers attended to the potential signal frequencies, particularly the highest signal frequency. With a signal cue, observers appeared to attend to the frequency of the subsequent signal.

Adult↗

PubMed2004

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.

Acoustic Stimulation↗