Exploring the front fricative contrast in Greek: A study of acoustic variability based on cepstral coefficients

Abstract

In the current study, we explore the factors underlying the well-known difficulty in acoustic classification of front nonsibilant fricatives (Maniwa, Jongman & Wade 2009, McMurray & Jongman 2011) by applying a novel classification method to the production of Greek speakers. The Greek fricative inventory [f v θ ð s z ç ʝ x ɣ] includes voiced and voiceless segments from five distinct places of articulation. Our corpus contains all of the Greek fricatives produced by 29 monolingual speakers, but our focus is on the distinction between the front nonsibilant fricatives [f v θ ð]. For comparison, we also discuss the other places of articulation where relevant. We apply a relatively novel classification method based on cepstral coefficients, previously successful in categorizing English obstruent bursts (Bunnell, Polikoff & McNicholas 2004), English vowels (Ferragne & Pellegrino 2010), Romanian fricatives (Spinu & Lilley 2016), and Russian fricatives (Spinu, Kochetov & Lilley 2018). For this study, fricative boundaries were automatically aligned using Hidden Markov Models (HMMs) and then manually checked. Six Bark-frequency cepstral coefficients (c0–c5) were extracted from 20-millisecond Hann windows. HMMs were used to divide the fricatives and adjacent vowels into three regions of internally minimized variance. A multinomial logistic regression analysis then used the mean cepstral coefficients from each region as predictors for classification by consonant identity. Our method yields highly successful classification rates, exceeding the performance of previous methods. We discuss these results in light of the differences of the phonemic distributions of fricatives between English and Greek.

Voicing neutralization in Romanian fricatives across different speech styles

“…Since they were 'borrowed' from the speech processing literature into linguistic studies, cepstral coefficients have proven to be an informative measure regarding the strength of various types of contrasts [9], including the voicing contrast in fricatives. Thus, cepstral coefficients were previously successful in categorizing English obstruent bursts [10], English vowels [11], Romanian fricatives [12,13], Russian sibilant fricatives [14], Azerbaijani fricatives [15], and Greek fricatives [16]. The potential advantages of using this measure in phonetic studies have been discussed extensively in recent literature.…”

“…MFCCs were used successfully in a study on the classification of voicing in fricatives in British English and European Portuguese [18]. Among other analyses conducted on a corpus of 1,522 intervocalic Greek fricatives produced by 29 monolingual speakers, [16] classified voicing in two pairs of front fricatives, labiodentals and interdentals, using Bark-scaled cepstral coefficients. The measures employed in this study were as follows: 18 measures obtained from the preceding vowel (6 cepstral coefficients × 3 tempo-ral regions), 18 measures from the fricative, and 6 measures from the first region of the vowel following the fricative.…”