What are we learning?

Our research activities

 

Below is a small sample of the research we have conducted at the Lions Voice Clinic. If you are interested in more details on the research that is done here, please contact our director, Dr. Deirdre D. Michael, Ph.D..

 

General Clinical Research

Perceptual and Acoustic Measures of Voice Quality

Perception of Singing Voice Quality

 


 

General Clinical Research

At the Lions Voice Clinic, we are called upon frequently to make educational presentations regarding all aspects of voice.  It is most helpful for us to have a library of voice recordings and videos of laryngeal examinations for use as examples in these presentations.  These audio and video samples might also be useful in research projects, so that we do not necessarily have to collect new research samples every time we begin a new project.  We invite our patients to assist us in these research and educational endeavors, by allowing us to use the data (information) that we collect during the normal course of their evaluation and treatment.  In order to do this, we have an ongoing general clinical study, approved by the University’s Institutional Review Board, that allows us to request permission for the use of these audio and video samples. 

Title: Measures of Vocal Production, Voice Quality, and Upper Airway Problems

Principal Investigators: Deirdre D. Michael, Ph.D., and George S. Goding, M.D., Department of Otolaryngology, University of Minnesota.

Co-Investigators and Personnel: Stephanie Misono, M.D., Lisa Butcher, M.M, M.A., Jesse Hoffmeister, M.S., Hiland Overgaard, B.M.

Human Subjects Code #: 0202M19041

Here is a portion of the consent form for that study:

     There are several kinds of research done in the Lions Voice Clinic. Research may be used to compare treatments or groups of patients.  It may also be used to determine how to best measure aspects of the voice, larynx, or airway.  We may use audio recordings to evaluate the sound of the voice and may take pictures of the larynx using endoscopy.  We may make other non-invasive measures of the function of the larynx.  Patients may also be asked questions about their voice or breathing problems as well as their opinions about treatment.  We may also seek judgments from teams of other experts.

     There are several kinds of educational activities carried out in the clinic.  We teach medical students, residents, graduate students from the department of Speech-Language Pathology, and students from the School of Music.  We also give educational presentations to colleagues and other professionals, as well as to the public.

     Information from evaluation and treatment of our patients is used for these research and educational activities.  However, no information about the identity of any patient is ever used in research or educational activities.  If we use your data, you will not be identified by name or in any other way.

     In certain circumstances, we may request that some portion of your audio or video recording be included on our website, www.lionsvoiceclinic.umn.edu.  If so, we would discuss the specific reasons with you, and ask you to place your initials on a separate line to designate your additional consent.  As with any consent, you would be free to change your mind at any time without affecting your relationship with us.

 

 

Perceptual and Acoustic Measures of Voice Quality

Below is the abstract for a paper we have written on this topic.

Title: Correlations Between Measures of Cepstral Peak Prominence,

Long-Term Average Spectrum, and Perceptual Ratings of Dysphonia in Persons with Glottic Incompetence

Authors: Deirdre D. Michael, Ph.D., Yolanda D. Heman-Ackah, M.D., and George S. Goding, Jr., M.D.

Presented at The Voice Foundation’s 30th Annual Symposium: Care of the Professional Voice; June 13-June 17, 2001

Introduction: Measures of cepstral peak prominence (CPP) have been shown to correlate with perceptual ratings of dysphonia more strongly than traditional measures of aperiodicity.  Cepstral peak prominence appears especially valuable in predicting overall grade of dysphonia and breathiness.  It appears less useful for predicting roughness, but has been shown to be more useful than measures of jitter and shimmer (Heman-Ackah, et al., 2000; Michael, 1998; Olson, et al., 1998).  Measures of the long-term average spectrum (LTAS) have also been shown to correlate well with perceptual ratings of breathiness and strain in samples of connected speech.  The current study compares perceptual ratings of overall dysphonia, roughness, breathiness, and strain with measures of CPP and LTAS. 

Methods:  Recordings of connected speech were obtained from patients with glottic incompetence of various etiologies.  These recordings were digitized using CSL hardware and software, then subjected to acoustic analysis using both CPP-s (CPP for connected speech) and CSL software.  Measures of CPP-s and CPPS-s (CPP with smoothing) were obtained.  LTAS measures were obtained using procedures described by Hammarberg (1986).  The recordings were also rated for degree of overall dysphonia, roughness, breathiness, and strain by trained speech-language pathologists.  Pearson correlation coefficients were used to compare CPP and LTAS measures to the perceptual ratings.

Results:  Results for the first set of 30 speech samples show CPP-s and CPPS-s to correlate moderately with ratings of overall grade of dysphonia (r = -.503, p = .004, and r = -.481, p = .0075 respectively) and with ratings of breathiness (r = -.572, p < .001, and r = -.403, p < .03, respectively).  Measures of CPPS-s also correlated with ratings of roughness (r = -.492, p = .006) and ratings of strain (r = -.378, p < .05).  None of the measures of LTAS correlated significantly with any of the measures of dysphonia. 

Conclusions:  Measures of CPP-s and CPPS-s are better predictors of overall grade of dysphonia and breathiness than are measures of LTAS, in samples of connected speech produced by persons with glottic incompetence.  In this study, LTAS was also not a good predictor of strain.

 

Perception of Singing Voice Quality

Below is the abstract for a paper we have written on this subject.

Title: Correlations Between Measures of Cepstral Peak Prominence, Long-Term Average Spectrum, and Perceptual Ratings of Singing Voice Quality

Authors:  Deirdre D. Michael, Ph.D., Susan Buesgens, M.A., Jennifer Swanson, M.M., Katherine Lindsay, B.A.

Presented at the 2nd International Physiology and Acoustics of Singing Conference, Denver, Colorado

October 7- October 9, 2004

Introduction:  An ongoing concern in the scientific study of voice is the quest for objective measures of voice quality that correlate with the “gold standard” of reliable perceptual ratings.  Acoustic measures have been used with varying degrees of success to quantify voice quality for dysphonic voices, but they have been used less often and less successfully to quantify singing voice quality.  This may be due both to the lack of acoustic measures and the difficulty obtaining reliable ratings of singing voice quality.

The acoustic measure of Cepstral Peak Prominence has been shown in numerous studies to correlate with measures of dysphonia, most especially the perceptual measure of “overall grade of dysphonia” in samples of voice ranging from normal to the most severely dysphonic.  This study examines the correlations of CPP with ratings of singing voice quality, ranging from normal to most supranormal. 

The acoustic measure of Long-term Average Spectrum (LTAS) has been used to measure singing voice quality, and has been moderately successful in correlating with ratings of dysphonic voice quality.  This study compares LTAS to CPP in quantifying singing voice quality.

 In studies of dysphonic voice quality, speech-language pathologists have shown high reliability in rating qualities of voice that are related to laryngeal function.  This study examines whether singing teachers can achieve the same level of reliability for ratings of singing voice quality, when using similar procedures. 

Methods:  Recordings of a vocalise and a passage from a song were recorded from singers ranging in proficiency from beginners to elite performers.  These recordings were subjected to CPP and LTAS analysis.  The samples were also rated for degree of overall quality of voice, breathiness, roughness, strain, and pitch stability by singing teachers.  Pearson correlation coefficients were used to compare CPP and LTAS measures to the perceptual ratings.

Results:  Results from a pilot study using 34 samples of singing rated by four singing teachers show that after a training procedure, the teachers’ ratings were highly and significantly correlated, so that a single average rating could be used to correlate with the CPP and LTAS ratings.  CPP measures correlated with ratings of breathiness, but generally not with the other perceptual ratings.  In general, LTAS measures correlated with ratings of breathiness and overall quality, and occasionally with measures of roughness and pitch stability. 

Discussion:  In this study, CPP was useful as a measure of breathiness, as opposed to studies of dysphonia in which it has correlated better with ratings of overall grade of dysphonia.  Measures of LTAS were also most useful in measuring breathiness.  The possible reasons for this are explored, as are the possible uses for these two measures in quantifying singing voice quality.

More importantly, in this study, singing teachers were able to differentiate a continuum of singers along parameters that are associated with laryngeal function and more typically used in ratings of dysphonia.  It is possible that those measures can serve as a point of departure in the ongoing quest for objective and reliable measures of singing voice quality.

 

 


 

 

Home | Who We Are | About The Voice | Voice Problems | Singers etc... | Related Problems | Research | Links | Index | Glossary

Deirdre D. Michael - micha008@umn.edu
To make an appointment, please call us at (612) 676-5717.