Comparison Study of Vocal Attack Time in Patients With Cleft Palate With and Without Glottal Stop in Mandarin.

Glottal stop (GS) is a typical compensatory articulation, which has a great impact on speech intelligibility in patients with cleft palate. It is usually detected by perceptual analysis. The aim of this study is to investigate the utility of vocal attack time (VAT) values in patients with cleft palate with and without GS, when unaspirated monosyllables are articulated in Mandarin, by using electroglottography. Unaspirated monosyllables /pa/ /pi/ /pu/ /ta/ /ti/ /tu/ /ka/ /ki/ /ku/ with tone one were analyzed. A total of 575 tokens were obtained from 42 patients with cleft palate, divided into a GS category (n = 312 tokens) and a nonglottal stop (NGS) category (n = 263 tokens), as assessed perceptually by three judges. Sound pressure and electroglottography recordings were also obtained from these tokens. The time lag of the cross-correlation function was used to gain VAT values. The results showed that the mean VAT values of tokens from the GS category (-0.25 ms) was significantly shorter than that of tokens in the NGS category (3.19 ms) (t = 7.326, P < 0.001). The results also showed that there was no significant difference in VAT values between the different combined monosyllables both in GS and in NGS group. The conclusion that can be drawn from this study is that the VAT value was sensitively decreased in cleft palate Mandarin speakers with GS comparing to those without GS.