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V M Richards

Publications and source records attributed to V M Richards.

23 records · Page 2Linked to original sources
PubMed1989

Auditory profile analysis: potential pitch cues.

The ability to detect changes in spectral shape, or profile analysis, was measured for both complex and simple changes in the power spectrum of a complex equal-amplitude standard. In an effort to determine whether detectability was mediated by changes in pitch that are concomitant with changes in spectral shape, the pitch of the stimuli were altered on a trial by trial basis. For moderate-range pitch randomizations, thresholds were on average 3 dB poorer than when no pitch randomization was employed. For large-range pitch randomizations, threshold changes were larger, but performance levels remained above chance levels. The psychophysical data, coupled with computer simulations of Feth's envelope-weighted average instantaneous frequency pitch model, indicate that changes in pitch contribute little to the discriminability of complex spectra.

Acoustic Stimulation↗
PubMed1989

Signal uncertainty and psychometric functions in profile analysis.

Experiment 1 was conducted to compare the effects of signal frequency uncertainty on the detection of a change in spectral shape and on the detection of a tone in wideband noise. Results indicate that for both tasks the uncertainty effect was small, being on average about 3 dB. In a second experiment, psychometric functions were measured for the detection of changes in the spectral shape of multicomponent complexes. Psychometric functions for profile tasks have a 25-dB range and are similar to those measured for the detection of an increment in the level of a single sinusoid. These psychometric functions are different from those found when detecting a signal in noise, which typically have a 10-dB range. Three equations for the shape of the psychometric functions were compared. The difference in the resulting fits was small, thus preventing an unambiguous choice of functional form.

Acoustic Stimulation↗
PubMed1988

Components of monaural envelope correlation perception.

The ability of listeners to discriminate between simultaneously presented bands of noise whose envelopes were either the same or statistically independent was determined. Bands of 100-Hz wide noise were employed which had low and high center frequencies of (2500, 2750), (2500, 3000), (2500, 3500) and (4000, 4400) Hz. Average discriminations were above 90% correct except for the (2500, 3500) Hz condition, which yielded an average of 77% correct. Next, a factorial stimulus design was employed in order to determine the relative importance of envelope and power spectrum cues. The results indicate that in the absence of power spectrum cues, bands with the same envelopes could be discriminated from bands with statistically independent envelopes. When the envelopes were always the same, listeners were able to discriminate between power spectra that were either the same or different. In contrast, when the envelopes were always different, listeners were unable to discriminate between the same and different power spectra.

Cues↗
PubMed1987

Monaural envelope correlation perception.

The ability to discriminate between simultaneously presented 100-Hz-wide bands of noise with envelopes that were either similar or dissimilar was measured. The center frequencies of the noise bands, fL and fL + delta f Hz, were systematically varied. When the bands of noise were separated by an octave, delta f = fL, discriminations were at chance levels. For frequency separations less than an octave, delta f less than fL, discrimination was best for fL = 2500 and 4000 Hz, somewhat poorer for fL = 1000 Hz, and impossible for fL = 350 Hz. Listeners were also asked to discriminate between bands of noise with envelopes that were either perfectly or partially correlated, and bands with envelopes that were either uncorrelated or partially correlated. The data suggest that, when transformed to an equal-variance scale (Fisher's z), equal changes in Fisher's z lead to equal changes in detectability, regardless of the correlation of the envelopes of the reference signal.

Acoustic Stimulation↗