Biomedical subjects

Zhongzhou Tang

Publications and source records attributed to Zhongzhou Tang.

3 recordsLinked to original sources

PubMed2006

Estimates of effective frequency selectivity based on the detection of a tone added to complex maskers.

In Experiment 1, the validity of parameters associated with the roex(p, r) auditory filter shape was examined for three different types of maskers: (a) A noise masker, (b) a random 12-tone masker whose frequencies varied on a burst-by-burst basis [multiple-burst different (MBD)], and (c) a random 12-tone masker whose frequencies were the same across bursts [multiple-burst same (MBS)]. First, the power spectrum model of masking was used to estimate auditory filter shapes for four observers. Second, the resulting auditory filter shapes were used in a computer simulation that provided an estimate of internal noise for each observer. Third, relative weights across frequency were estimated for each observer and each masker type. For the noise masker, these analyses provided predictions and relative weights that were consistent across the three analyses. For the MBD and MBS maskers, there was little consistency; neither the estimated internal noise nor the estimated relative weights reliably supported a single-filter model of detection. In Experiment 2, the time course for the detection of a tone added to an MBD masker was evaluated by estimating relative weights jointly in time and frequency. The relative weights at the signal frequency formed a rough inverse "U" across time.

Acoustic Stimulation↗

PubMed2003

Examination of a linear model in an informational masking study.

When multitone maskers are used in a two-interval, forced choice experiment, the amount of masking is larger when the masker is randomly chosen on each presentation interval compared to on each trial (the same masker in the two listening intervals). These conditions are referred to as having within- versus between-trial randomization. If it is assumed that an observer's ultimate detection decision depends on a single decision variable (DV), it is probable that the DV's variance will be substantially larger in the within-trial randomization condition compared to the between-trial randomization condition. The goal of the current experiment is to evaluate the degree to which this stimulus-based change in DV variance can account for the difference in thresholds in the within-versus between-trial randomization conditions. Thresholds are measured for the detection of a tone added to a six-component masker in between- and within-trial randomization conditions. The slopes of the psychometric functions provide an estimate of the variance in the DV for the between- and within-trial randomization conditions. Additionally, a channel model is fitted to the psychophysical results in the within-trial randomization condition. The resulting model is then used to predict the value of the DV for each trial, and ultimately to estimate the proportion of the total variance in the within-trial randomization condition that is attributable to changes in maskers across intervals. The variance of the DV in the between-trial randomization condition accounted for approximately 65% of the total variance in the DV in the within-trial randomization condition. Stimulus-based interval-by-interval masker randomization accounted for approximately 20% of the total variance of the within-trial randomization DV. The remaining 15% of the DV variance in the within-trial randomization condition remained unaccounted for. This result is fairly stable whether the maskers are drawn from a small versus large pool of potential maskers.

Attention↗

PubMed2002

Informational masking with small set sizes.

Informational masking refers to interference in the detectability of a sound, or discrimination of some property of a sound, beyond that which can be attributed to interactions at the auditory periphery. In the current experiments the signal to be detected was a tone added to a 6-tone masker, and informational masking was introduced by randomly choosing the frequencies of the tones that comprise the masker. The primary question was whether small numbers of maskers could replace randomly drawn maskers without sacrificing the underlying detection schemes adopted by observers. Similar to the method used by Wright and Saberi [J. Acoust. Soc. Am. 105, 1765-1775 (1999)], detection thresholds were measured for different masker set sizes, where set size refers to the number of 6-tone maskers from which any one masker was drawn. Set sizes of 3, 6, 12, and 24 were tested as well as conditions in which the maskers were chosen at random. In addition, observers' memory for maskers was coarsely evaluated. Large differences in thresholds were found across observers and across different masker sets. Even for set sizes of 24, the memory test suggests some recognition of maskers for some observers. Post hoc analysis of the data included an evaluation of the relative contribution of different frequencies using a single linear model. As a base for comparison, a linear model fitted to each condition was also evaluated. Although the data were fitted better using many rather than one linear model, the reduction in quality of fit was modest. This result suggests substantial consistency in decision strategies regardless of masker set size.

Adult↗