Recognition and Classification of Pauses in Stuttered Speech using Acoustic Features

Pauses plays an essential role in speech activities. Normally it helps the listener by creating a time and space to decode and interpret the message of a speaker. But in case of stuttering pauses disturbs the normal flow of speech. The uncontrolled, frequent and unplanned occurance of pasuses leads to slow speaking rate, results in broken words and increases the severity level of stuttering. Hence pauses and stuttering has a close relationship. Pauses are considered as one of the important pattern in diagnoisis and treatment of stuttering. In this work, an attempt has been made for the identification of inaudible (Silent or Unfilled) pauses from stuttered speech. The attributes like duration, frequency, position and distribution of pauses during speech tasks are measured and quantified. UCLASS stuttered speech corpus is considered for the analysis. Automatic blind segmentation approach is adopted to segment the speech signal into voice and unvoiced regions using dynamic threshold set based on energy and zero crossing rate (ZCR). 4th formant frequencies are analysed to identify intra-morphic (unfilled) pauses present within voiced regions. The duratiion of intra-morphic pauses are analysed for stuttred speech and normal speech. It is observed that the duration of normal intramorphic pause ranges from 150 ms-250 ms and inter-morphic pauses are <=250 ms and short pause have duration ranges from 50 ms-150 ms. Whereas in stuttering short intra-morphic pauses ranges from 10 ms to 50 ms, long pauses ranges from 250 ms to 1 or 2 seconds. Segmentation of the intra-morphic pauses is observed to acheive an accuracy of 98%. Results are compared and validated with manual method.