Acoustic voice analysis by means of the hoarseness diagram

The hoarseness diagram (Michaelis, Fröhlich, & Strube, 1998a) has been proposed as a new approach to describe different acoustic properties of voices. To test its performance in the analysis of pathologically disturbed and normal voices five requirements are suggested that should be met by any acoustic voice-analysis protocol to be used in voice research and clinical practice. The hoarseness diagram is then tested with regard to these requirements. Individual voices are found to show a satisfactory localization in the diagram. Aspects of stationarity are discussed in the context of four case studies. The different cases illustrate that changes in the acoustic analysis results are observed if the voice-generation conditions change, whereas results are stationary if phonation conditions do not change. Different pathological voice groups defined on grounds of the specific phonation mechanism are found to map to specific regions of the hoarseness diagram, with differences between group locations being significant. All results can be interpreted without exceptions if the two hoarseness diagram coordinates are taken to reflect the vibrational irregularity of the voice-generation mechanisms on the one side and the degree of closure of the vibrating structures on the other side. The hoarseness diagram and its underlying algorithms are thus shown to constitute a useful approach to acoustic voice analysis in research and clinical practice. The tests themselves demonstrate several application possibilities, including the quantitative monitoring of individual voices.