Capturing Breathy Voice: Durational Measures of Oral Stops in Marathi

Abstract

The present study investigates a series of techniques used to capture the durational differences of oral stops in Marathi, an Indic language that exhibits a four-way phonemic distinction among oral stops. Like many of its Indic relatives, Marathi utilizes both voicing and aspiration to achieve oral stop contrasts, yielding aspirated and plain versions of both voiced and voiceless stops. While voice onset time (VOT) is an acoustic feature which can be reliably used to distinguish between plain voiced, plain voiceless, and aspirated voiceless stops, it does not help to differentiate between plain voiced and aspirated voiced—or breathy-voiced—stops. While durational differences may not be sufficient in and of themselves, they do contribute acoustic cues that aid in establishing the four-way contrast. With this in mind, the present production study investigates the utility of two alternative acoustic measures of duration that have been proposed: Noise Offset Time (NOT), proposed by Davis (1994), is measured from the release burst to the beginning of the second formant in the following vowel. The After Closure Time (ACT), proposed by Mikuteit and Reetz (2007), is measured from the release burst to the beginning of periodicity in the waveform. Six native speakers of Marathi were recorded producing a randomized word-list that contained Marathi oral stops in word-initial position before [a]. The digitized recordings were fed into PRAAT, and waveforms and spectrograms were used to measure the ACT and the NOT of each stop. While there is some utility to each measurement, this study suggests that neither is completely clear cut; speaker variation means that the hallmarks of the waveform or spectrogram consulted to take each measurement are sometimes absent or open to subjectivity. A new measurement that takes advantage of the consistently present elements of both the ACT and the NOT is proposed. This measure, referred to as the Pre-vocalic Interval (PVI), is measured from the release burst to the jump in intensity which coincides with the appearance of clear formants in the spectrogram of the following vowel.