Biomedical subjects

K L Landahl

Publications and source records attributed to K L Landahl.

3 recordsLinked to original sources

PubMed1995

Comparison of fundamental frequency and perturbation measurements among three analysis systems.

The need for standardization of procedures in approaches to voice measurement has been recently emphasized. The purpose of this study was to determine the extent to which the acoustic perturbation measurements from three different analysis systems agree when standardized recording and analysis procedures are used. High-quality acoustic voice recordings from 20 patients were analyzed. The results showed that, although fundamental frequency measurements were in strong agreement among the three systems tested, frequency and amplitude perturbation measurements were not in agreement. The underlying approaches to perturbation measurement appeared to be sufficiently different to produce different results. An argument is made for a standardized set of acoustic signals representing normal, dysphonic, and synthesized voices with known characteristics to facilitate testing of new acoustic analysis systems and confirm measurement accuracy and sensitivity.

Adolescent↗

PubMed1982

Acoustic invariance and the perception of place of articulation: a selective adaptation study.

Two adaptation experiments were conducted exploring the perception of place of articulation in stop consonants. We hope to determine whether in making a phonetic decision about place of articulation, the perceptual system is sensitive to subtle changes in the fine structure of a CV stimulus (i.e. onset formant frequencies and transition motions) when both the adapting and test stimuli shared the same invariant properties. These invariants are defined in terms of the gross spectral shape at stimulus onset. In the first experiment, the effects of adaptors varying in duration (full CV syllables or shortened CV syllables called onsets), vowel context ([a] versus [i]), onset formant frequencies, and presence or absence of moving transitions were tested on CV [ba da ga] test stimuli. All adaptors contained sufficient information to extract the invariant properties for place of articulation based on spectral shape at consonant release. Results showed that the various onsets did not adapt full CV [ba da ga] test stimuli. In the second experiment, the effects of the onset adaptors were tested on onset CV [ba da ga] test stimuli. Results showed that onsets can adapt an onset place of articulation continuum in a manner similar to place of articulation adaptation using full CV syllables. Further, the fine structure of the stimuli significantly affected the adaptation results. Finally, vowel contingency effects seem to reflect differences in onset frequencies of the consonants in CV syllables rather than the steady-state frequencies of the following vowels.

Adult↗

PubMed1981

Abnormal laryngeal vocal quality in ectodermal dysplasia.

Breathy vocal quality was verified in five of nine patients with the ectrodactyly--ectodermal dysplasia--cleft palate syndrome, nine of 15 patients with either suspected or confirmed anhidrotic ectodermal dysplasia (one case of partial expression), and one of two siblings with the Rapp-Hodgkin form of ectodermal dysplasia. Indirect laryngoscopy in eight of the breathy patients failed to show phonatory glottal chinks or any overt laryngeal pathologic conditions, but it did indicate absence of a normal mucosal covering of the folds. Limited spectrographic studies disclosed widely spaced voicing striations and also suggested prolonged voice onset times. Patients who exhibit breathy vocal quality in the presence of one of these ectodermal dysplasias should be counseled with regard to the advisability of longitudinal care and the avoidance of habitual use of increased vocal effort level.

Child↗