Collinearity and Sample Coverage Issues in the Objective Measurement of Vocal Quality: The Case of Roughness and Breathiness Purpose The aim of the study was to address the reported inconsistencies in the relationship between objective acoustic measures and perceptual ratings of vocal quality. Method This tutorial moves away from the more widely examined problems related to obtaining the perceptual ratings and the acoustic measures and centers ... Tutorial
Tutorial  |   January 22, 2018
Collinearity and Sample Coverage Issues in the Objective Measurement of Vocal Quality: The Case of Roughness and Breathiness
 
Author Affiliations & Notes
  • Carlos A. Ferrer
    Electrical Engineering Faculty, Central University of Las Villas, Santa Clara, Cuba
    Department of Computer Science, University Erlangen-Nuremberg
  • Tino Haderlein
    Department of Computer Science, University Erlangen-Nuremberg
  • Youri Maryn
    Department of Otorhinolaryngology and Head and Neck Surgery, European Institute for ORL, Sint-Augustinus General Hospital, Antwerp, Belgium
  • Marc S. de Bodt
    Department of Communication Disorders, Antwerp University Hospital, Edegem, Oost Vlaanderen, Belgium
  • Elmar Nöth
    Department of Computer Science, University Erlangen-Nuremberg
  • Disclosure: The authors have declared that no competing interests existed at the time of publication.
    Disclosure: The authors have declared that no competing interests existed at the time of publication. ×
  • Correspondence to Carlos A. Ferrer: cferrer@uclv.edu.cu
  • Editor-in-Chief: Julie Liss
    Editor-in-Chief: Julie Liss×
  • Editor: Jack Jiang
    Editor: Jack Jiang×
Article Information
Speech, Voice & Prosodic Disorders / Voice Disorders / Hearing & Speech Perception / Acoustics / Speech / Tutorial
Tutorial   |   January 22, 2018
Collinearity and Sample Coverage Issues in the Objective Measurement of Vocal Quality: The Case of Roughness and Breathiness
Journal of Speech, Language, and Hearing Research, January 2018, Vol. 61, 1-24. doi:10.1044/2017_JSLHR-S-17-0136
History: Received April 13, 2017 , Revised June 26, 2017 , Accepted July 27, 2017
 
Journal of Speech, Language, and Hearing Research, January 2018, Vol. 61, 1-24. doi:10.1044/2017_JSLHR-S-17-0136
History: Received April 13, 2017; Revised June 26, 2017; Accepted July 27, 2017

Purpose The aim of the study was to address the reported inconsistencies in the relationship between objective acoustic measures and perceptual ratings of vocal quality.

Method This tutorial moves away from the more widely examined problems related to obtaining the perceptual ratings and the acoustic measures and centers in less scrutinized issues regarding the procedure to establish the correspondence. Expressions for the most common measure of association between perceptual and acoustic measures (Pearson's r) are derived using a multiple linear regression model. The particular case where the multiple linear regression involves only roughness and breathiness is discussed to illustrate the issues.

Results Most problems reported regarding inconsistent findings in the relationship between given acoustic measures and particular perceptual ratings could be linked to sample properties not directly related to the actual relationship. The influential sample properties are the collinearity between the regressors in the multiple linear regression and their relative variances. Recommendations on how to rule out this possible cause of inconsistency are given, varying in scope from data collection, reporting, manipulation, and results interpretation.

Conclusions The problems described can be extended to more general cases than the exemplified roughness and breathiness sample's coverage. Ruling out this possible cause of inconsistency would increase the validity of the results reported.

Acknowledgment
This article was funded in part by a fellowship granted by the Alexander von Humboldt Foundation to the first author (Ref 3.2-1164728-CUB-GF-E).
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