Analysis of acoustic-phonetic variations in fluent speech using TIMIT

We propose a hierarchically structured analysis of variance (ANOVA) method to analyze, in a quantitative manner, the contributions of various identifiable factors to the overall acoustic variability exhibited in fluent speech data of TIMIT processed in the form of mel-frequency cepstral coefficients. The results of the analysis show that the greatest acoustic variability in TIMIT data is explained by the difference among distinct phonetic labels in TIMIT, followed by the phonetic context difference given a fixed phonetic label. The variability among sequential sub-segments within each TIMIT-defined phonetic segment is found to be significantly greater than the gender, dialect region, and speaker factors. Our results serve to provide useful insights to the understanding of the roles of various components of speech recognizers in contributing to the ultimate speech recognition performance