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Acoustic and Aerodynamic Assessment: A Historical Compendium from the Journal of Voice
Phonation is the result of aerodynamic forces acting on the vocal fold tissue subsequent to their positioning within the direct path of an expired air stream. The aerodynamic forces cause the vocal folds to oscillate and modulate the air stream. This modulation creates acoustic energy we refer to as “voice”. A foundational belief among voice therapists and laryngologists is that the skilled ear of a clinician and/or physician when used for auditory-perceptual assessment is a critical tool for the evaluation and management of voice disorders. Auditory-perceptual assessments, however, are by their nature subjective. They are prone to variability from one listener to the next, and perceptual thresholds for what constitutes a “normal” voice from a “dysphonic” voice, and the degree of dysphonic severity, also vary. These are among the reasons why instrumental assessments are also considered valuable and sometimes critical tools for the assessment and management of dysphonic patients.
Along with laryngeal endoscopy - the most important instrumental assessment applied to dysphonic patients - acoustic and aerodynamic assessments of vocal function provide information corresponding to underlying laryngeal physiology. The patterns of acoustic energy, airflow through the glottis, and pressures below the glottis are influenced by the neuromuscular coordination, configuration, and oscillatory movement of the vocal folds. Typically, when a voice changes from a perceptual state of normal to dysphonic or vice versa, the acoustic spectrum and underlying aerodynamic forces also change. Acoustic and aerodynamic assessments allow for objective measurement of these changes and are not influenced by the perceptual experience of a listener, potential perceptual bias, or the variability in perceptual calibration which affect auditory-perceptual assessments.
From its inception the Journal of Voice has been a primary repository of new and expanded knowledge of the acoustic and aerodynamic characteristics of normal and disordered voice production. Among the authors who have contributed to these publications include internationally recognized leaders in clinical voice science and practice across more than four decades. The articles included in this compendium relate to both the speaking and singing voice in normal and disordered states. While page limitations do not allow for a complete reference of all articles published in this journal, the following collection of historical publications include those which have expanded our understanding of acoustic and aerodynamic characteristics of voice in a majority of the treatment-seeking and non-treatment seeking populations served by speech-language pathology and medicine.
Across the volumes included in this collection the reader will find articles illuminating knowledge of acoustic and aerodynamic expectations in (a) normal voice production, (b) vocal development in children, (c) non-organic voice disorders, (d) vocal aging, (e) mid-membranous lesions, (f) vocal fold paralysis, (g) spasmodic dysphonia and essential voice tremor, and many other conditions causing dysphonia. In addition, the articles identified in this collection include many which have helped us understand how the larynx controls and is affected by singing. Many of these articles have also provided evidence of how the singing voice responds to medical and behavioral treatment, and the effectiveness of different voice therapy and surgical interventions for varied etiologies of dysphonia.
In reviewing this collection it would be reasonable to suggest that the Journal of Voice has served as the preeminent source for scientific evidence related to clinical voice science for the past thirty years. Articles published in this journal continue to inform evidence-based practice and enlighten knowledge of the human speaking and singing voice. It is my hope that this collection provides a resource for professionals in addition to stimulating ideas for future research. It has been a rewarding experience trolling through the past issues of this journal, and it is my hope that the reader will find value in this robust collection of knowledge associated with acoustic and aerodynamic assessments of voice.
Christopher R. Watts, Ph.D., CCC-SLP
ASHA Fellow
Director, Davies School of Communication Sciences & Disorders
Texas Christian University
Fort Worth, TX
Aerodynamic Patterns in Patients With Voice Disorders: A Retrospective Study
A recently published retrospective chart review of aerodynamic profiles of women with primary muscle tension dysphonia by Gillespie et al (2013) identified various relationships between mean airflow rate (MFR) and estimated subglottal pressure (est-Psub). The current retrospective study expanded the diagnostic categories to include all voice disorders referred for voice therapy. Three research questions were proposed: (1) Are there differences in the MFR and the est-Psub compared with the normal control group? (2) Within the disordered population, are there different variations in the pairing of MFR and est-Psub? (3) If these variations exist, are they diagnosis specific?Pitch Strength as an Outcome Measure for Treatment of Dysphonia
Measurement of treatment outcomes is critical for the spectrum of voice treatments (ie, surgical, behavioral, or pharmacological). Outcome measures typically include visual (eg, stroboscopic data), auditory (eg, Consensus Auditory-Perceptual Evaluation of Voice; Grade, Roughness, Breathiness, Asthenia, Strain), and objective correlates of vocal fold vibratory characteristics, such as acoustic signals (eg, harmonics-to-noise ratio, cepstral peak prominence) or patient self-reported questionnaires (eg, Voice Handicap Index, Voice-Related Quality of Life).Measuring the Dysphonia Severity Index (DSI) in the Program Praat
The original Dysphonia Severity Index (ie, DSI) weighs and combines four voice markers in a single number to size dysphonia gradation in the clinic: percent jitter (from Multi-Dimensional Voice Program; KayPENTAX Corp., Montvale, NJ), softest intensity and highest fundamental frequency (both from Voice Range Profile; KayPENTAX Corp.), and maximum phonation time. To be more generally applied, however, implementation of DSI in the program Praat (Paul Boersma and David Weenink, Institute for Phonetic Sciences, University of Amsterdam, The Netherlands) would be advantageous for all voice clinicians.The Acoustic Breathiness Index (ABI): A Multivariate Acoustic Model for Breathiness
The evaluation of voice quality is a major component of voice assessment. The aim of the present study was to develop a new multivariate acoustic model for the evaluation of breathiness.Resonance Tube or Lax Vox?
This study compares the flow resistance of Resonance tube (RT) and Lax Vox tube (LVT) when submerged 2 cm and 10 cm in water, as well as phonation into the tubes in these conditions.A Formant Range Profile for Singers
Vowel selection is important in differentiating between singing styles. The timbre of the vocal instrument, which is related to its frequency spectrum, is governed by both the glottal sound source and the vowel choices made by singers. Consequently, the ability to modify the vowel space is a measure of how successfully a singer can maintain a desired timbre across a range of pitches. Formant range profiles were produced as a means of quantifying this ability. Seventy-seven subjects (including trained and untrained vocalists) participated, producing vowels with three intended mouth shapes: (1) neutral or speech-like, (2) megaphone-shaped (wide open mouth), and (3) inverted-megaphone-shaped (widened oropharynx with moderate mouth opening).A Comparison of Cepstral Peak Prominence Measures From Two Acoustic Analysis Programs
This study aimed to investigate the relationship and reliability of cepstral peak prominence (CPP) measures from two acoustic software applications, Analysis of Dysphonia in Speech and Voice (ADSV) and Praat.Immediate Effects of the Vocal Function Exercises Semi-Occluded Mouth Posture on Glottal Airflow Parameters: A Preliminary Study
The study aimed to quantify immediate alterations in the airflow glottogram between the Vocal Function Exercises semi-occluded mouth posture (/ol/ with lip buzz) and the sustained vowel /o/ in individuals with normal voices, and to determine if noted changes were in agreement with established semi-occluded vocal tract aerodynamic theory. Based on semi-occluded vocal tract aerodynamic theory, we hypothesized the following immediate changes in the flow glottogram during the /ol-buzz/ condition: a greater open quotient, a greater skewing quotient, a greater maximum flow declination rate, increased average airflow, decreased peak airflow, and increased minimum airflow.Lax Vox as a Voice Training Program for Teachers: A Pilot Study
The objective of this study was to explore the effectiveness of a 3-week training program with the voice therapy “Lax Vox” for teachers.Pre- and Poststimulation Study on the Phonatory Aerodynamic System on Participants with Dysphonia
The purpose of this preliminary investigation was to examine the sensitivity of the Phonatory Aerodynamic System (PAS) in an exploratory investigation that looked at the effects of stimulation training (pre and post stimulation) on 20 participants with vocal complaints. The following parameters were tested: subglottal pressure, sound pressure level, airflow, and fundamental frequency.Phonation Quotient in Women: A Measure of Vocal Efficiency Using Three Aerodynamic Instruments
The purpose of this study was to examine measures of vital capacity and phonation quotient across three age groups in women using three different aerodynamic instruments representing low-tech and high-tech options.Characterization of Flow-resistant Tubes Used for Semi-occluded Vocal Tract Voice Training and Therapy
This study aimed to characterize the pressure-flow relationship of tubes used for semi-occluded vocal tract voice training/therapy, as well as to answer these major questions: (1) What is the relative importance of tube length to tube diameter? (2) What is the range of oral pressures achieved with tubes at phonation flow rates? (3) Does mouth configuration behind the tubes matter?Spectral Measures of Hoarseness in Persons with Hyperfunctional Voice Disorder
The purpose of the present investigation was to understand the spectral differences between individuals with hyperfunctional voice disorders and subjects with normal voice in terms of H1-H2, H1-A1, H1-A2, and H1-A3 (H1, first harmonic amplitude; H2, second harmonic amplitude; A1, amplitude of the most robust harmonic in the region of first formant frequency; A2, amplitude of the strongest harmonic component in the region of second formant frequency; A3, amplitude of the most robust harmonic component in the region of third formant frequency).Validation of the Cepstral Spectral Index of Dysphonia (CSID) as a Screening Tool for Voice Disorders: Development of Clinical Cutoff Scores
The purposes of this study were to (1) evaluate the performance of the Cepstral Spectral Index of Dysphonia (CSID—a multivariate estimate of dysphonia severity) as a potential screening tool for voice disorder identification and (2) identify potential clinical cutoff scores to classify voice-disordered cases versus controls.Aerodynamic Outcomes of Four Common Voice Disorders: Moving Toward Disorder-Specific Assessment
The two goals of the present study were to (1) determine the ability of commonly used aerodynamic voice measures to capture change as a function of known interventions and (2) determine if certain aerodynamic measures demonstrate better responsiveness to change in specific disorder types than others.Glottal Adduction and Subglottal Pressure in Singing
Previous research suggests that independent variation of vocal loudness and glottal configuration (type and degree of vocal fold adduction) does not occur in untrained speech production. This study investigated whether these factors can be varied independently in trained singing and how subglottal pressure is related to average glottal airflow, voice source properties, and sound level under these conditions. A classically trained baritone produced sustained phonations on the endoscopic vowel [i:] at pitch D4 (approximately 294 Hz), exclusively varying either (a) vocal register; (b) phonation type (from “breathy” to “pressed” via cartilaginous adduction); or (c) vocal loudness, while keeping the others constant.Cepstral Peak Sensitivity: A Theoretic Analysis and Comparison of Several Implementations
The aim of this study was to develop a theoretic analysis of the cepstral peak (CP), to compare several CP software programs, and to propose methods for reducing variability in CP estimation.Relationship Between Subglottal Pressure and Sound Pressure Level in Untrained Voices
Subglottal pressure (Ps) is strongly correlated with sound pressure level (SPL) and is easy to measure by means of commonly available equipment. The SPL/Ps ratio is strongly dependent on the efficiency of the phonatory apparatus and should be of great relevance to clinical practice. However, published normative data are still missing.The Flow and Pressure Relationships in Different Tubes Commonly Used for Semi-occluded Vocal Tract Exercises
This experimental study investigated the back pressure (Pback) versus flow (U) relationship for 10 different tubes commonly used for semi-occluded vocal tract exercises, that is, eight straws of different lengths and diameters, a resonance tube, and a silicone tube similar to a Lax Vox tube. All tubes were assessed with the free end in air. The resonance tube and silicone tube were further assessed with the free end under water at the depths from 1 to 7 cm in steps of 1 cm. The results showed that relative changes in the diameter of straws affect Pback considerably more compared with the same amount of relative change in length.Clinical Utility of CAPE-V Sentences for Determination of Speaking Fundamental Frequency
Sentence stimuli from the Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) were compared with standard speaking fundamental frequency (SF0) tasks to establish clinical utility of the sentence stimuli for standardized assessment of SF0.An Aerodynamic Study of Phonations in Patients With Parkinson Disease (PD)
The precise comparison of the voice characteristics of Parkinson disease (PD) patients with age-matched normal subjects is still one of the important research projects. The present study aimed at comparing the voice characteristics in sustained phonations of PD patients with an age-matched control group.Multidimensional Voice Data on Participants With Perceptually Normal Voices From Ages 60 to 80: A Preliminary Acoustic Reference for the Elderly Population
The purpose of this study was to provide a preliminary acoustic reference for an elderly population (aged 60–80) with perceptually normal voices to determine the degree of noise in the vocal signal of this population; a younger population (aged 20–30) with perceptually normal voices participated for comparison. The participants were tested on the MultidimensionalVoice Program (model 5105, KayPENTAX, Lincoln Park, NJ), and the following acoustic parameters were evaluated: relative average perturbation (cycle-to-cycle frequency perturbations), shimmer (cycle-to-cycle amplitude perturbations), and noise-to-harmonic ratio (degree of noise in the vocal signal).Objective Dysphonia Measures in the Program Praat: Smoothed Cepstral Peak Prominence and Acoustic Voice Quality Index
A version of the “smoothed cepstral peak prominence” (ie, CPPS) has recently been implemented in the program Praat. The present study therefore estimated the correspondence between the original CPPS from the program SpeechTool and Praat's version of the CPPS. Because the CPPS is the main factor in the multivariate Acoustic Voice Quality Index (AVQI), this study also investigated the proportional relationship between the AVQI with the original and the second version of the CPPS.A Preliminary Investigation of Potential Biases in Phonation Threshold Pressure Analysis
Phonation threshold pressure (PTP) is a voice measure used in both research and clinic. PTP data analysis is susceptible to bias from investigator awareness of experimental hypothesis, and poor investigator training. The objective of this study was to systematically examine the role of these two biases on PTP data analysis.The Effect of Stretch-and-Flow Voice Therapy on Measures of Vocal Function and Handicap
To investigate the efficacy of stretch-and-flow voice therapy as a primary physiological treatment for patients with hyperfunctional voice disorders.
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