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L Demany

Publications and source records attributed to L Demany.

7 recordsLinked to original sources
PubMed1992

Detection of inharmonicity in dichotic pure-tone dyads.

Thresholds for the detection of quasi-sinusoidal frequency ratio fluctuations were measured with stimuli consisting of dichotic dyads of simultaneous pure tones. The two component tones of each dyad were slowly modulated in frequency, in such a way that the ratio of their instantaneous frequencies oscillated (or not) around some standard frequency ratio (SFR). As in a previous study [Demany and Semal (1988) J. Acoust. Soc. Am. 83, 687-695], it was found that smaller oscillations could be detected when the SFR was precisely an octave (2/1) than when it was slightly smaller or larger (2/1 +/- 50 or 100 cents). Similar 'harmonicity effects' were obtained here for SFRs in the vicinity of a fifth (3/2), a twelfth (3/1), or a double octave (4/1). However, these harmonicity effects were generally less pronounced than those observed in the vicinity of an octave. Each of our four subjects provided evidence for a central sensitivity to the octave harmonicity, but the same consistency could not be found with respect to other kinds of harmonicity.

Acoustic Stimulation↗
PubMed1991

Dissociation of pitch from timbre in auditory short-term memory.

In three experiments, untrained listeners made same/different judgments on pairs of pure or complex tones with periods that eventually differed by +/- 4%. On each trial, the two test tones were separated by 4.3 s, during which other tones (I) were heard but had to be ignored. The period (p) of the first test tone was randomly selected between 1/600 and 1/300 s. The period of each I tone was randomly selected among four possible values, close to p (+/- 3% or 6% apart) in some conditions, and remote from p in other conditions. In addition, from condition to condition, the spectral content of the I tones was varied independently of their periods: The I tones could have the same harmonic content as the test tones, or a very different harmonic content. Subjects' performances were much better when the periods of the I tones were remote from p than when they were close to p, as expected from previous findings by D. Deutsch [e.g., Science 175, 1020-1022 (1972)]. But, more importantly, the relation between the spectral contents of the I tones and the test tones had, by itself, practically no effect on performance. Thus performance was affected by the pitches of the I tones, but not by their timbres. These results suggest that pitch is processed independently of timbre in auditory short-term memory.

Adult↗
PubMed1990

Harmonic and melodic octave templates.

For normal-hearing adult listeners, two simultaneous pure tones with a frequency ratio close to 2/1 may perceptually fuse into a single sound, which shows that such listeners are sensitive to "octave harmony." Many adult listeners are also able to consistently adjust two successive pure tones "one octave apart," which shows that they possess melodic octave templates. According to Terhardt [J. Acoust. Soc. Am. 55, 1061-1069 (1974)], melodic octave templates and the perception of octave harmony originate from a common learning process taking place in early life. In the two experiments reported here, subjects performed repeated octave adjustments for pairs of simultaneous and successive tone bursts. Both tones were presented monaurally, at 45 or 65 dB SPL. The frequency of the lower tone (fref) was an independent variable, while the frequency of the higher tone was adjustable within a 500-cent range. In some conditions, when the two tones were presented simultaneously, they were sinusoidally frequency modulated in a coherent manner, at a rate of 2 or 4 Hz; the aim of this frequency modulation was to force the subjects to adopt a synthetic listening strategy, i.e., to base their adjustments on perceived harmony. For fref values ranging from 270-2000 Hz, subjects performed consistent adjustments when the tones were presented successively: fref had little effect on the adjustments' variability. However, in the same frequency range, the variability of the harmonic adjustments markedly increased with fref; for the highest fref values, it was much greater than the variability of the melodic adjustments. The results suggest that, in adult listeners, the perception of octave harmony disappears at frequencies for which melodic octaves are still accurately perceived.

Adult↗
PubMed1990

The effect of vibrato on the recognition of masked vowels.

Five experiments on the identifiability of synthetic vowels masked by wideband sounds are reported. In each experiment, identification thresholds (signal/masker ratios, in decibels) were measured for two versions of four vowels: a vibrated version, in which FO varied sinusoidally around 100 Hz; and a steady version, in which F0 was fixed at 100 Hz. The first three experiments were performed on naive subjects. Experiment 1 showed that for maskers consisting of bursts of pink noise, vibrato had no effect on thresholds. In Experiment 2, where the maskers were periodic pulse trains with an F0 randomly varied between 120 and 140 Hz from trial to trial, vibrato slightly improved thresholds when the sound pressure level of the maskers was 40 dB, but had no effect for 65-dB maskers. In Experiment 3, vibrated rather than steady pulse trains were used as maskers; when these maskers were at 40 dB, the vibrated versions of the vowels were slightly less identifiable than their steady versions; but, as in Experiment 2, vibrato had no effect when the maskers were at 65 dB. Experiment 4 showed that the unmasking effect of vibrato found in Experiment 2 disappeared in subjects trained in the identification task. Finally, Experiment 5 indicated that in trained listeners, vibrato had no influence on identification performance even when the maskers and the vowels had synchronous onsets and offsets. We conclude that vibrating a vowel masked by a wideband sound can affect its identification threshold, but only for tonal maskers and in untrained listeners. This effect of vibrato should probably be considered as a Gestalt phenomenon originating from central auditory mechanisms.

Adult↗
PubMed1989

Detection thresholds for sinusoidal frequency modulation.

An adaptive forced-choice procedure was used to measure, in four normal-hearing subjects, detection thresholds for sinusoidal frequency modulation as a function of carrier frequency (fc, from 250 to 4000 Hz) and modulation frequency (fmod. from 1 to 64 Hz). The results show that, for a wide range of fmod values, fc and fmod have almost independent effects on the thresholds when the thresholds are expressed as just-noticeable frequency swings and plotted on a log scale. In two subjects, the effect of fc on the thresholds was compared to the effect of standard frequency on the frequency just noticeable differences (jnd's) of successive and steady tones. In agreement with previous data [H. Fastl, J. Acoust. Soc. Am. 63, 275-277 (1978)], it was found that the two effects are significantly different if the frequency jnd's are measured with long-duration tones. However, it was also found that the two effects are similar if the frequency jnd's are measured with 25-ms tones. These results support the idea that, at least for low fmod values, the detection of continuous and periodic frequency modulations is mediated by a pitch-sampling process using a temporal window of about 25 ms.

Adult↗
PubMed1988

Dichotic fusion of two tones one octave apart: evidence for internal octave templates.

Stimuli consisting of two simultaneous and sinusoidally frequency-modulated pure tones were dichotically presented to four listeners. Two component tones of each stimulus were approximately an octave apart. They were both modulated at 2 Hz, and the frequency swing resulting from each modulation corresponded to one tenth of the carrier frequency. The listeners' task was to detect phase differences between the modulation waveforms of the two simultaneous tones: With an adaptive 2IFC procedure, just-noticeable values of phi, the phase angle of the modulation waveforms, were measured as a function of the interval formed by the carrier frequencies (one octave, i.e., 1200 cents, +/- 0, 25, 50, or 100 cents). When the carrier frequencies were not too high, just-noticeable values of phi often varied nonmonotonically with the interval, showing a minimum at or near 1200 cents. An additional experiment indicated that most, if not all, of these octave effects were not due to some form of beat detection. As a whole, the results reported here provide evidence for the existence of internal octave templates. Such templates might play an important role in the perceptual segregation of simultaneous harmonic signals, as well as in pitch perception.

Acoustic Stimulation↗