Biomedical subjects

A H Takeuchi

Publications and source records attributed to A H Takeuchi.

5 recordsLinked to original sources

PubMed1995

Effect of frequency transposition on the discrimination of amplitude envelope patterns.

The effects of systematic training on listeners' ability to compare the amplitude envelopes of signals differing in frequency was tested. Listeners indicated which of two comparison signals had the same amplitude envelope as the target signal. During training, center frequencies of comparison signals were gradually increased or decreased relative to target signal center frequencies of 500, 1600, and 3160 Hz. After training, performance was still worse when target and comparison signals were at different frequencies rather than at the same frequency, except possibly when comparison signals were higher in frequency than the 1600-Hz target. Thus the amplitude envelopes of signals do not appear to be perceived independently of the signal itself. Listeners who received no training performed similarly to the trained listeners, except that their performances declined when comparison signals were higher in frequency than the 1600-Hz target. Training did not reduce interlistener differences in overall performance or in the extent of the decline in performance when frequency differences between the target and comparison signals were introduced. The effects of frequency lowering on amplitude envelope discrimination do not appear to be related to the reduced efficacy of frequency-lowered speech-derived amplitude envelopes in supplementing speechreading.

Adolescent↗

PubMed1995

Recognition of amplitude-modulation patterns in the presence of a distractor. I. Effects of correlation and frequency relation.

Listeners' ability to compare the amplitude modulation pattern of 200- and 500-Hz targets when distractors that were also amplitude modulated were presented simultaneously was evaluated. The amplitude modulations of the distractors were either uncorrelated, partially correlated, or fully correlated with the amplitude modulations of the comparisons. Relative to the case of no distractor, performance tended to decrease when a distractor was present, and the degree of interference increased as the modulation correlation between the comparisons and distractors decreased. Although the interference was greater when the comparisons and distractors were separated by 50 Hz, there was also significant interference when the separation was 300 Hz. Whether the comparison was higher or lower in frequency than the distractor had no overall effect. However, the effect of modulation correlation was greater when comparisons were higher than distractors rather than lower. Patterns of interference are compared to those found in studies of modulation detection and discrimination interference, and implications for the use of multiple-band signals that carry the amplitude envelopes from different spectral regions of a speech signal to convey speech are discussed.

Auditory Perception↗

PubMed1995

Recognition of amplitude-modulation patterns in the presence of a distractor. II. Effects of dichotic presentation and unmodulated distractors.

Listeners indicated which of two comparisons had the same pattern of amplitude modulation as a target signal when distractors were presented simultaneously with the comparisons. The frequency separation between distractors and comparisons was either narrow or wide. Distractors were either modulated independently of the comparisons, comodulated with the comparisons, or unmodulated. At wide frequency separations, none of the distractors interfered significantly with modulation comparison, relative to performance with no distractors. At narrow frequency separations, comodulated distractors produced less interference than did independently modulated distractors. Unmodulated distractors also produced some interference. There was no difference between diotic presentation and dichotic presentation, in which distractors were presented to the opposite ear from targets and comparisons. Implications for the presentation of multiple envelope signals derived from different spectral regions of a speech signal to convey speech to hearing-impaired listeners are discussed.

Auditory Perception↗

PubMed1994

Maximum key-profile correlation (MKC) as a measure of tonal structure in music.

Tonal structure is musical organization on the basis of pitch, in which pitches vary in importance and rate of occurrence according to their relationship to a tonal center. Experiment 1 evaluated the maximum key-profile correlation (MKC), a product of Krumhansl and Schmuckler's key-finding algorithm (Krumhansl, 1990), as a measure of tonal structure. The MKC is the maximum correlation coefficient between the pitch class distribution in a musical sample and key profiles, which indicate the stability of pitches with respect to particular tonal centers. The MKC values of melodies correlated strongly with listeners' ratings of tonal structure. To measure the influence of the temporal order of pitches on perceived tonal structure, three measures (fifth span, semitone span, and pitch contour) taken from previous studies of melody perception were also correlated with tonal structure ratings. None of the temporal measures correlated as strongly or as consistently with tonal structure ratings as did the MKC, and nor did combining them with the MKC improve prediction of tonal structure ratings. In Experiment 2, the MKC did not correlate with recognition memory of melodies. However, melodies with very low MKC values were recognized less accurately than melodies with very high MKC values. Although it does not incorporate temporal, rhythmic, or harmonic factors that may influence perceived tonal structure, the MKC can be interpreted as a measure of tonal structure, at least for brief melodies.

Algorithms↗

PubMed1993

Absolute pitch.

Absolute pitch (AP) is the ability to identify a tone's pitch or to produce a tone at a particular pitch without the use of an external reference pitch. AP exists in varying degrees among people generally described as AP possessors. AP possessors vary not only in the accuracy with which they can identify pitches but also in their ability to produce pitches absolutely and in their ability to identify tones of various timbers and in various pitch registers. AP possessors' memory for pitches is mediated by verbal pitch names; they do not have superior memory for pitches per se. Although the etiology of AP is not yet completely understood, evidence points toward the early-learning theory. This theory states that AP can be learned by anyone during a limited period early in development, up to about age 6, after which a general developmental shift from perceiving individual features to perceiving relations among features makes AP difficult or impossible to acquire.

Aptitude↗