Perceptual and acoustic reliability estimates for the Speech Disorders Classification System (SDCS)

A companion paper describes three extensions to a classification system for paediatric speech sound disorders termed the Speech Disorders Classification System (SDCS). The SDCS uses perceptual and acoustic data reduction methods to obtain information on a speaker's speech, prosody, and voice. The present paper provides reliability estimates for the two perceptual methods (narrow phonetic transcription; prosody-voice coding) and the acoustic analysis methods the SDCS uses to describe and classify a speaker's speech competence, precision, and stability. Speech samples from 10 speakers, five with significant motor speech disorder and five with typical speech, were re-measured to estimate intra-judge and inter-judge agreement for the perceptual and acoustic methods. Each of the speakers completed five speech tasks (total = 50 datasets), ranging in articulatory difficulty for the speakers, with consequences for the difficulty level of data reduction. Point-to-point percentage of agreement findings for the two perceptual methods were as high or higher than reported in literature reviews and from previous studies conducted within the laboratory. Percentage of agreement findings for the acoustics tasks of segmenting phonemes, editing fundamental frequency tracks, and estimating formants ranged from values in the mid 70% to 100%, with most estimates in the mid 80% to mid 90% range. Findings are interpreted as support for the perceptual and acoustic methods used in the SDCS to describe and classify speakers with speech sound disorders.