A Comparison of Speech Intelligibility Measures Between Unsophisticated Listener Judgements and Orthographic Transcription

Intelligible speech is a primary component for successful communication. However, the speech of children with disordered phonologies is often unintelligible. Therefore, when assessing the speech intelligibility of children in order to determine whether they qualify for intervention services, speech-language pathologists need reliable evaluation tools. The focus of this investigation was the measurement of speech intelligibility. The purpose of this study was to examine the relationship between two methods for measuring speech intelligibility. The first, identification method, involves the listener transcribing a speech sample from which the percentage of words understood is calculated. The second, scaling procedure, involves the listener estimating the percentage of words understood from a continuous speech sample. The secondary purpose of this study was to examine the accuracy of the scaling method as measured by ear estimation compared to the identification method as measured through orthographic transcription for each of three groups of children with: (a) the most intelligibility, (b) average intelligibility, and (c) least intelligibility. Four unsophisticated listeners rated the speech intelligibility of 48 speakers aged 4:0 to 5:6 who comprised three groups with varying levels of phonological proficiency. The listeners who were unfamiliar with the speakers, but familiar with the topic, rated the children\u27s continuous speech samples using ear estimation. The data collected were then compared with intelligibility ratings as measured in a previous study via orthographic transcription. The two methods of measuring speech intelligibility examined in this study were found to be positively correlated (r = .86). However, the t-test analysis revealed significant differences between the two measures for the most and least intelligible groups, indicating discrepancies between the two methods when measuring the speech intelligibility of some children. Additional statistical analysis revealed poor intrajudge reliability which should be considered when interpreting the results presented. It does appear, however, that when measuring speech intelligibility, using ear estimation, is reflective of the orthographic transcription measure, although the actual estimated percentages of intelligibility appear to differ from the percentages derived from orthographic transcription