Search PubMed⌕ Search

Biomedical subjects

R N Ohde

Publications and source records attributed to R N Ohde.

27 records · Page 2Linked to original sources
PubMed1984

Effect of formant frequency onset variation on the differentiation of synthesized /w/ and /r/ sounds.

The purpose of this study was to assess the use of psychophysical transformations for analyzing the differentiation of /w/ and /r/ sounds of children and adults. Stimuli from Adult and Child manifolds, consisting of 25 synthesized /Cej/-type utterances with different F2 and F3 onset frequencies, were presented in random order to eight naive subjects. Subjects rated the stimuli on a four-point scale between good /r/ and good /w/. Correlations between mel transformations and Bark transformations of the F3-F2 differences among the stimuli and their percent /r/ responses were close to or greater than .90. Predictions of percent /r/ responses derived from regression analyses based on mel transformations and Bark transformations of F3-F2 differences among stimuli indicated that some sounds identified as /w/ for /r/ substitutions could be differentiated from /w/ sounds. The category boundaries between /r/ and /w/ were estimated to be 5.0 Bark for adult stimuli and 5.7 Bark for child stimuli.

Adult↗
PubMed1984

Fundamental frequency as an acoustic correlate of stop consonant voicing.

Fundamental frequency (F0) and voice onset time (VOT) were measured in utterances containing voiceless aspirated /ph,th,kh/, voiceless unaspirated /sp,st,sk/, and voiced /b,d,g/ stop consonants. Although VOT was very similar for voiceless unaspirated and voiced stops, F0 contours were nearly identical for voiceless unaspirated and voiceless aspirated stops, and both types of voiceless stops were associated with significantly higher F0 values than were voiced stops. The F0 contours in all context were generally falling; the data do not support a simple rise-fall dichotomy in F0 at voicing onset as an invariant acoustic correlate of the voicing feature. The variations in F0 as a function of voicing appear to be best accounted for by vocal cord tension rather than aerodynamic influences. Moreover, the results are consistent with physiological data showing that the position of the hyoid bone and the height of the larynx influence the absolute value of F0.

Humans↗
PubMed1983

Perception of distorted "R" sounds in the synthesized speech of children and adults.

Adult and Child manifolds were generated by synthesizing 5 X 5 matrices of /Cej/ type utterances in which F2 and F3 frequencies were systematically varied. Manifold stimuli were presented to 11 graduate-level speech-language pathology students in two conditions: (a) a rating condition in which stimuli were rated on a 4-point scale between good /r/ and good /w/; and (b) a labeling condition in which stimuli were labeled as "R," "W," "distorted R," or "N" (for none of the previous choices). It was found that (a) stimuli with low F2 and high F3 frequencies were rated 1.0-1.4; those with high F2 and low F3 frequencies were rated 3.6-4.0 were labeled as "R"; (c) none of the Child manifold stimuli were labeled as distorted "R" and one of the Adult manifold stimuli approached a level of identification that approached the percentage of identification for "R" and "W"; and (d) rating and labeling tasks were performed with a high degree of reliability.

Adult↗
PubMed1983

Effect of burst amplitude on the perception of stop consonant place of articulation.

We have examined the effects of the relative amplitude of the release burst on perception of the place of articulation of utterance-initial voiceless and voiced stop consonants. The amplitude of the burst, which occurs within the first 10-15 ms following consonant release, was systematically varied in 5-dB steps from -10 to +10 dB relative to a "normal" burst amplitude for two labial-to-alveolar synthetic speech continua--one comprising voiceless stops and the other, voiced stops. The distribution of spectral energy in the bursts for the labial and alveolar stops at the ends of the continuum was consistent with the spectrum shapes observed in natural utterances, and intermediate shapes were used for intermediate stimuli on the continuum. The results of identification tests with these stimuli showed that the relative amplitude of the burst significantly affected the perception of the place of articulation of both voiceless and voiced stops, but the effect was greater for the former than the latter. The results are consistent with a view that two basic properties contribute to the labial-alveolar distinction in English. One of these is determined by the time course of the change in amplitude in the high-frequency range (above 2500 Hz) in the few tens of ms following consonantal release, and the other is determined by the frequencies of spectral peaks associated with the second and third formants in relation to the first formant.

Humans↗
PubMed1981

Stop identification from vocalic transition plus vowel segments of CV and VC syllables: a follow-up study.

In a recent article in the Journal [L. C. W. Pols and M. E. H. Schouten, J. Acoust. Soc. Am. 64, 1333-1337 (1978)], it was concluded that perception experiments which present CV syllables with the consonant bursts deleted invoke a "click sensation" and that this sensation has a deleterious affect on the perception of the consonants. In order to directly assess the "click sensation" hypothesis, a computer-based speech editing system was used which smooths onsets and offsets of stimuli and therefore eliminates the possibility of an acoustic click. Subjects identified voiced and voiceless stops from vocalic transition + vowel stimuli edited from CV and VC syllables. The findings were as follows: (1) Consonant identification from vocalic transition + vowel segments in VC syllables was significantly greater than that from vocalic transition + vowel segments in CV syllables; and (2) The superiority of the scores for VC vocalic transition + vowel segment was found for both voiced and voiceless stops, but it was not as great for voiced stops. Although there are differences in magnitude of findings between this study and those which employed other deletion techniques, the reliability and direction of the results were similar. The results do not support the "click sensation"hypothesis and suggest that other mechanisms must account for differences between CV and VC syllables in the perception of sound segments.

Follow-Up Studies↗
PubMed1980

Effects of number of repetitions and intensity level of stimuli varying in VOT on verbal transformations.

The purpose of this study was to investigate the perception of transformations by varying the voice onset time (VOT) of the repeating stimulus, its repetition number, and intensity level. Fifteen subjects rated the 5-, 25-, and 55-ms VOT stimuli during periods of repetitions so that transformations could be identified according to their place and voicing characteristics. The number of stimulus repetitions was 5, 32, or 95, and the sound-pressure level of the repeating stimulus was 50, 70, or 90 dB. The major findings were as follows (1) The 90-dB level condition produced significantly more transformations than either the 50- or 70-dB conditions for the 55-ms stimulus only; (2) A significant difference in number of transformations was obtained for each paired copmparison of the 55-ms stimulus, but only between the 5-, 32-, and 95- repetition pairs for the 5 and 25 ms stimuli; and (3) Significant correlations were obtained between the voiceless and alveolar features of transformations for the 55-ms stimulus, and between the voiced, alveolar, and velar features of transformations for the 5- and 25-ms stimuli. The findings support a transformation process sensitive to voicing and place cues and a peripheral component of transformations.

Acoustic Stimulation↗
PubMed1979

Relationship between adaptation and the percept and transformations of stop consonant voicing: effects of the number of repetitions and intensity of adaptors.

Important issues in selective adaptation research concern the relative contribution of response related (perceptual) and stimulus related (acoustic) effects of the adaptor in the adaptive process. Two response related issues pertain to the effects of the adaptor percept and verbal transformations on adaptation. This investigation systematically examined perceptual and acoustic contributions of the adaptor on the adaptation of the voicing feature. Subjects rated the degree of voicing/voicelessness of end-point VOT adaptors, i.e., 5- and 55-ms VOT, and an acoustically neutral adaptor, i.e., 25-ms VOT, during periods of repetitions. The number of adaptor repetitions during each of ten trials was either 5, 32, or 95, and the intensity of the adapting stimulus was either 50, 70, or 90 dB SPL. The major findings were as follows: (1) No significant correlations were found between ratings of voicing percept of the adaptor and magnitude of boundary shift; (2) Increases in repetitions and relative intensity level of end-point adaptors produced significantly greater phonetic boundary shifts and generally greater affects on ratings of test stimuli; and (3) The end-point adaptors produced significant shifts in rating of boundary and nonboundary stimuli. The findings indicate that neigher the adaptor percept or verbal transformations affected the magnitude of adaptation. These results and those for acoustic parameters strongly suggest an acoustic as opposed to a phonetic basis of adaptation of the voicing feature. Furthermore, the effects of end-point adaptors on boundary and nonboundary stimuli support the generalized change in feature sensitivity assumed by a fatigue model of adaptation.

Acoustic Stimulation↗
PubMed1977

Order effect of acoustic segments of VC and CV syllables on stop and vowel identification.

The purpose of this study was to determine the importance of the vocalic transition relative to other acoustic cues in the perception of both CV and VC syllables. Subjects identified stops, /p, t, k, b, d, g/ and vowels, /i, u, 3/ from the aperiodic, aperiodic + vocalic transition, vocalic transition, and vocalic transition + vowel segments edited from VC and CV syllables. The major findings were as follows: (1) no significant difference was found in consonant identification scores between aperiodic, aperiodic + vocalic transition, and vocalic transition segments in CV syllables compared to those in VC syllables; (2) consonant identifications from vocalic transition + vowel segments in VC syllables were significantly greater than those from vocalic transition + vowel segments in CV syllables; (3) no significant difference was found in vowel identification scores between aperiodic + vocalic transition, vocalic transition + vowel, and vocalic transition segments in CV syllables compared to those in VC syllables; and (4) vowel identifications from aperiodic segments were significantly greater in CV syllables than in VC syllables. The results revealed a significant right-to-left perceptual advantage for both vowels and consonants. The findings for consonant identification emphasize the importance of the temporal order relationship between the vocalic transition and steady-state vowels in the perceptual process.

Acoustics↗