Maximum Flow Declination Rate Research Articles

Group differences in measures of voice production and revised values of maximum airflow declination rate

In previous reports, aerodynamic and acoustic measures of voice production were presented for groups of normal male and female speakers [Holmberg et al., J. Acoust. Soc. Am. 84, 511-529 (1988); J. Voice 3, 294-305 (1989)] that were used as norms in studies of voice disorders [Hillman et al., J. Speech Hear. Res. 32, 373-392 (1989); J. Voice 4, 52-63 (1990)]. Several of the measures were extracted from glottal airflow waveforms that were derived by inverse filtering a high-time-resolution oral airflow signal. Recently, the methods have been updated and a new study of additional subjects has been conducted. This report presents previous (1988) and current (1993) group mean values of sound pressure level, fundamental frequency, maximum airflow declination rate, ac flow, peak flow, minimum flow, ac-dc ratio, inferred subglottal air pressure, average flow, and glottal resistance. Statistical tests indicate overall group differences and differences for values of several individual parameters between the 1988 and 1993 studies. Some inter-study differences in parameter values may be due to sampling effects and minor methodological differences; however, a comparative test of 1988 and 1993 inverse filtering algorithms shows that some lower 1988 values of maximum flow declination rate were due at least in part to excessive low-pass filtering in the 1988 algorithm. The observed differences should have had a negligible influence on the conclusions of our studies of voice disorders.

Comparison of Aerodynamic and Electroglottographic Parameters in Evaluating Clinically Relevant Voicing Patterns

The purpose of the present study was to identify one or more aerodynamic or electroglottographic measures that distinguish among voicing patterns that are clinically relevant for nodule pathogenesis and regression: a presumably pathogenic pattern (pressed voice), a neutral pattern (normal voice), and two presumably therapeutic patterns (resonant voice and breathy voice). Trained subjects with normal voices produced several tokens of each voice type on sustained vowels /a/, /i/, and /u/. For each token, maximum flow declination rate, alternating current flow, and minimum flow were obtained from inverse-filtered airflow signals, and closed quotient and closing time were obtained from electroglottographic signals. The results indicate that for /a/ and /i/ (but not for /u/), the closed quotient provides a sensitive tool for distinguishing the voice types in physiologically interpretable directions. Further, post-hoc analyses confirmed a direct relationship between the closed quotient and videoscopic ratings of laryngeal adduction, which previous work links to nodule pathogenesis and regression.

Respiratory and laryngeal measures of children during vocal intensity variation

Simultaneous aerodynamic, acoustic, and kinematic measurements from the laryngeal and respiratory systems were made in order to study mechanisms for changing vocal intensity. Aerodynamic and acoustic measures include an approximation of open quotient, maximum flow declination rate, alternating glottal airflow, estimated tracheal pressure, sound pressure level, and fundamental frequency. Respiratory measures included lung volume, rib cage, and abdominal displacements. Adults were used as a comparison group to twenty 4-year-olds and twenty 8-year-olds. Laryngeal and respiratory results indicate that speech production differences between the children and adults are based both on size and function. For example, children's absolute anteroposterior diameters of the rib cage are smaller than adults, but their rib cage movement is larger and encompasses a different range during speech breathing. Since children are functionally different than adults, age specific speech production models need to be developed.

Aerodynamic and acoustic changes following intensive voice therapy for patients with Parkinson’s disease: A case study

A 50‐year‐old patient with Parkinson’s disease received a 4‐week course of intensive voice and respiratory therapy aimed at improving functional communication through increased laryngeal adduction. Aerodynamic and acoustic data were gathered on two occasions before treatment, two after the completion of therapy, and at 6‐ and 12‐month follow‐up sessions. There were increases in subglottal pressure and laryngeal airway resistance after the treatment. Maximum flow declination rate (MFDR) also increased, as did the sound pressure level of utterances that the subject produced at a ‘‘comfortable’’ effort level. Fundamental frequency variability and conversational intensity levels were higher post therapy. Video‐stroboscopic examination before and after treatment showed improvements in adduction and a decreased level of supraglottic hyperfunction. Possible physiological mechanisms are discussed to account for these changes. [Work supported by NIH Grant No. R01 DC01150‐03 and NIDCD Grant No. DC00976.]

Respiratory and Laryngeal Function of Women and Men During Vocal Intensity Variation

Simultaneous procedures for making aerodynamic and kinematic observations of the laryngeal and chest wall systems were used to investigate variations in vocal intensity in normal women and men. Laryngeal results indicate that significant increases of maximum flow declination rate and laryngeal airway resistance and significant decreases in open quotient occur when higher intensity levels are produced. Respiratory results indicate that tracheal pressure, percent rib cage contribution, lung volume, and rib cage volume initiations are higher, and lung and rib cage volume excursions are larger when higher vocal intensity levels are produced. Laryngeal and respiratory function results indicate that some measures are different for women than for men. Mean data support the notion that increases in tracheal pressure are achieved by inhaling to higher lung and rib cage volumes. Individual subject data provide alternative respiratory and laryngeal patterns for changing the shape of the glottal airflow waveform.

On the existence of speaker-specific maximum flow declination rate (MFDR)–sound pressure level (SPL) profiles.

Oral flow was registered with a Rothenberg mask in two male subjects during the utterance of an /æ/ vowel embedded in a word at three intensity levels (soft, normal, and loud voice), and during the production of crescendos and decrescendos on the same vowel at three fundamental frequencies. Registered signals were digitized and processed with specific hard- and software [J. S. Perkell, J. Acoust. Soc. Am. 89, 1777–1781 (1991)] to give the MFDR. This is a measure for the decrease of airflow through the glottis, during the closing phase of the glottal cycle. MFDR values showed a speaker-specific relationship with SPL. To explore this specificity, MFDR values were measured in 70 subjects during phonation of the vowel /æ/ with soft, normal, and loud voice. The relation between MFDR and SPL can be described with MFDR=a+bSPL. The dependency of the parameters a and b on gender, voice training, and vocal pathology will be discussed. [Support was given by the Foundation for Linguistic Research, NWO.]

Voice quality of Amoy falling tones.

The two Amoy falling tones−high falling and low falling−have long and short versions. The short versions occur in syllables with ‘‘entering tone’’−i.e., syllables that are closed by final unaspirated stops [p, t, k, glottal stop]. The shorter duration and the final unaspirated stop are well known to be the major cues for identifying entering tone. In this study, voice quality is examined as a possible minor cue. Oral and nasal air flow were recorded in word pairs contrasting short- and long-falling tones. The oral air flow data were inverse filtered, and maximum ac flow, minimum ac flow, maximum flow declination rate, and durations of open and closed phases were measured. Preliminary results suggest that there is less nasal flow in the short versions by comparison to the long (perhaps reflecting a simultaneous glottal stricture in the syllable-final voiceless stop), but there seems to be no other phonation contrast.

Objective assessment of vocal hyperfunction: an experimental framework and initial results.

This report describes the experimental design and initial results of an ongoing clinical investigation of voice disorders. Its major focus is the development and use of quantitative measures to provide objective descriptions of conditions referred to as "vocal hyperfunction." The experimental design for this project is based on a descriptive theoretical framework, which holds that there are different types and stages of hyperfunctionally related voice disorders. Data consist of indirect measures derived from noninvasive aerodynamic and acoustic recordings including (a) parameters derived from inverse filtered approximations of the glottal air flow waveform; (b) estimates of transglottal pressure, average glottal air flow, glottal resistance and vocal efficiency; and (c) measures of vocal intensity and fundamental frequency. Initial results (based on comparisons among 15 voice patients and 45 normal speakers) support major assumptions that underlie the theoretical framework, and indicate that the measurement approach being utilized is capable of differentiating hyperfunctional from normal voices and hyperfunctional conditions from one another. Organic manifestations of vocal hyperfunction (nodules, polyps, contact ulcers) are accompanied by abnormally high values for the glottal waveform parameters of AC flow and maximum flow declination rate, suggesting increased potential for vocal fold trauma due to high vocal fold closure velocities and collision forces. In contrast, nonorganic manifestations of hyperfunction (functional disorders) tend to be associated with abnormally high levels of unmodulated DC flow, without high values for AC flow and maximum flow declination rate, suggesting reduced potential for vocal fold trauma. Measures also suggest different underlying mechanisms for nodules and polyps as compared to contact ulcers. Results are discussed relative to predictions based on the theoretical framework for vocal hyperfunction.