Biomedical subjects

M C Picardi

Publications and source records attributed to M C Picardi.

3 recordsLinked to original sources

PubMed1983

Successive versus simultaneous comparison in auditory intensity discrimination.

The ability to discriminate between two brief sounds having identical frequency components, but differing in the intensity of one or more of the components, is studied. The stimulus manipulations include randomizing the overall intensity of the sounds, varying the number and spacing of the components, and varying the interval of time between the sounds. The results from the experiment in which interstimulus interval is manipulated clearly support a profile analysis mechanism that computes two rough spectral analyses, stores a classification of these spectra in memory, and compares the two stores. This profile mechanism involves a simultaneous comparison of different components of the complex, some remote from the signal frequency, rather than a successive comparison of the difference in intensity at the signal frequency. The simultaneous comparison process is more sensitive when the profile is composed of many components spaced over a wide frequency range.

Discrimination, Psychological↗

PubMed1981

Psychophysical tuning curves independent of signal level.

Psychophysical tuning curves were obtained for three subjects in a forward masking paradigm, with signal levels of 21, 30, and 50 dB SPL at 1000 Hz and 30, 40, and 50 dB SPL with a 3000-Hz signal. All tuning curves were measured in quiet and with a background noise adjusted to produce a constant signal-to-noise ratio of E/N0 = 16 dB. The results indicated that the tuning curves obtained in quite change shape with increasing signal level, whereas the shapes of tuning curves measured in noise are the same at all signal levels. A control condition demonstrates that only signal energy in a narrow band near the signal frequency is useful in detecting the signal. This control along with the invariance of tuning curve shape with signal level support the interpretation that the broadening of tuning curves with increased signal level, observed when the signals are presented in quiet, is caused by the presence of off-frequency components.

Acoustic Stimulation↗

PubMed1981

Signal and masker uncertainty in intensity discrimination.

Intensity discrimination thresholds were assessed in a series of experiments. Signals were in-phase increments in the level of one component of a multitone masker. The main parameters of interest were the effects of signal uncertainty (which frequency is tested on a given trial) and masker uncertainty (which components were selected as the multitone masker on a given trial). Thresholds were measured as a function of signal frequency, number of components, and amount of overall changes in masker level. The results suggest a form of profile processing, in which the signal is detected by comparing levels in adjacent critical bands. Such a mechanism will account for the relatively small effects generally observed with signal uncertainty, for masker uncertainty showing larger effects on thresholds than signal uncertainty, and for the near constancy of signal threshold despite large (60 dB) fluctuations in overall level of the stimulus in the two intervals of the forced-choice trial.

Acoustic Stimulation↗