Impact of Speaking Rate on the Source Filter Interaction in Speech: A Study

Source filter interaction (SFI) explains the drop in pitch caused due to the constriction in the vocal tract during voiced consonant production in a vowel-consonant-vowel (VCV) sequence. In this work, we examine how the drop in pitch alters when such a VCV sequence is spoken at three different speaking rates - slow, normal and fast. In the absence of electroglottograph (EGG) recording, a high resolution pitch contour is determined using a glottal closure instant (GCI) detector. For this, in this work, firstly, five different GCI detector and pitch estimation techniques are compared against EGG based pitch estimates on a small dataset where simultaneous EGG recordings are available. Yet Another GCI Algorithm (YAGA) is found to be the best choice among all. For examining the impact of speaking rate on SFI, VCV recordings from six subjects with five vowels (/a/, /e/, /i/, /o/, /u/) and five consonants (/b/, /d/, /g/, /v/, /z/) at three speaking rates are used. The study reveals a significant difference in the pitch drop values between slow and fast rates, with increasing pitch drop as speaking rate reduces. For slow speaking rate, vowel /o/ and /u/ tend to show higher pitch drop values compared to remaining vowels.