Effect of Dynamic Time Warping on Alignment of Phrases and Phonemes

Abstract

Speech synthesis and recognition are the basic techniques used for man -machine communication. This type of communication is valuable when our hands and eyes are busy in some other task such as driving a vehicle, performing surgery, or firing weapons at the enemy. Dynamic time warping (DTW) is mostly used for aligning two given multidimensional sequences. It finds an optimal match between the given sequences. The distance between the aligned sequences shouldbe relatively lesser as compared to unaligned sequences. The improvement in the alignment may be estimated from the corresponding distances. This technique has applications in speech recognition, speech synthesis, and speaker transformation. The objective of this research is to investigate the amount of improvement in the alignment corresponding to the sentence based and phoneme based manually aligned phrases. The speech signals in the form of twenty five phrases were recorded from each of six speakers (3 m ales and 3 females). The recorded material was segmented manually and aligned at sentence and phoneme level. The aligned sentences of different speaker pairs were analyzed using HNM and the HNM parameters were further aligned at frame level using DTW. Mahalanobis distances were computed for each pair of sentences. The investigations have shown more than 20 % reduction inthe average Mahalanobis distance s.