SST 2010 Phonation in Sumi Nasals Tom Harris1 1 School of Languages and Linguistics, University of Melbourne, Australia [email protected] Abstract 2. Background A key feature of Sumi phonology is a distinctive Sreedhar [7, 8] identified two phonemically distinct forms of breathy/modal voicing contrast in its bilabial and alveolar the bilabial nasal and the alveolar nasal in Sumi. These nasals. Using contrastive phonation on nasals is rare cross- distinct forms he labeled unaspirated and aspirated voiced linguistically, but relatively common in Tibeto-Burman forms, and suggested they exist as a phonemicised sequence languages. Research using instrumental techniques to provide of the nasal in question and the glottal fricative /h/. In this detailed descriptions of the articulatory and acoustic paper, this distinction is labeled a breathy/modal one, and the properties of breathy nasals in Tibeto-Burman languages is nasals investigated are transcribed as /m/, /mh/, /n/ and /nh/. limited. In this study, breathy nasals were investigated using Here 'breathy' refers to the characteristic of having 'breathy a combination of airflow and laryngographic analyses. They voice', known also as 'murmur' [9] or as 'voiced aspiration' were found to comprise an initial, ‘non-breathy’ segment, and [4]. A velar nasal also exists in Sumi, although a a following ‘breathy’ segment demonstrating increased breathy/modal contrast is not made at this place of airflow and voicing patterns typical of breathy voice. articulation. Sreedhar [7, 8] also posits an allophonic variant Index Terms: phonation, breathy voice, Tibeto-Burman, of the alveolar nasal, being a palatal nasal existing before articulatory phonetics front vowels. It is suggested that this variant has a breathy/modal contrast, however, remarkably few examples 1. Introduction of either breathy or modal palatal nasals existed in the data Sumi, also known as Sema, is a language of central and south recorded for this experiment, and it appears that the palatal Nagaland, India. A language of the Naga group of the Tibeto- nasals and alveolar nasals are in free variation. Burman family, Sumi is spoken by approximately 242,000 Breathy voice refers to one of only three manners people [1]. of phonation that are known to contrast meaningfully cross- A key feature of Sumi phonology is a distinctive linguistically. These three are: breathy, modal and creaky breathy/modal voicing contrast in its bilabial and alveolar voice, of which modal is the neutral setting to which the nasals. Cross-linguistically, languages with contrasting others are compared [10]. In Sumi, there appears to be a breathy and modal voiced sounds are rare, but those that phonemic contrast between breathy and modal settings. make such a contrast do so in stops, nasals, laterals and In modal phonation, there is 'regular, efficient vowels [2]. Hindi, for example, makes a four-way voicing vibration of the true vocal folds, without audible friction' [11] distinction in its stops, labeled 'voiceless unaspirated', (p.114). Tension is a factor in determining the vibration of 'voiceless aspirated', 'voiced' and 'voiced aspirated', the last of the vocal folds - modal phonation is typified by vocal folds these being known also as breathy voiced stops. The most having 'normal adductive and longitudinal tension' which distinctive breathy characteristic of Hindi breathy stops is the results in the vocal folds being apart for half of the glottal persisting voicing throughout the segment, with a greater cycle [10] (p.15). than expected increase in airflow immediately after the Variation from this setting is known as non-modal release of the stop [2]. phonation, of which breathy voice is one form. In breathy Gordon and Ladefoged [3] suggest that Hindi voice, the vocal folds are typically more abducted than in likewise makes a breathy contrast in its nasals, although it modal voice and have less longitudinal tension [3]. This should be noted that Esposito et al. [4] state that it is not clear results in less contact between the vocal folds and therefore a if /N/ + /h/ sequences in Hindi are in fact breathy nasals, or greater volume of turbulent airflow passing through the simply [Nh] clusters. Tibeto-Burman languages, such as glottis. The vocal folds 'flapping in the breeze' [11] (p.418), Sumi, also often contrast breathy voice in their nasal sounds. coupled with their continued vibration, gives the impression An example of this is in Newar, where a two-way of 'voice mixed in with breath' (Catford, in [3] (p.385)). breathy/modal contrast exists in the nasal series [5]. The The defining articulatory characteristic of breathy Khonoma dialect of Angami – a neighbouring language of voice, then, is the manner in which the vocal folds are held Sumi – similarly makes a two-way voicing contrast in its far more loosely than in modal voice. This leads to the vocal nasals [6], and although this is a voiceless/voiced contrast folds being open for a longer portion of the glottal cycle, and rather than a breathy voiced/modal voiced contrast, the making less complete contact on closure. The proportion of airflow and timing characteristic are very similar to those in the glottal cycle that the vocal folds are apart is known as the the breathy voiced/modal voiced contrast found in Sumi. Open Quotient [12], which can be determined by analysing This paper uses a combination of acoustic and the Lx signal from a laryngograph, a device that monitors articulatory measures to establish that the breathy/modal glottal activity non-invasively by measuring glottal voicing distinction in Sumi is characterized by differences in impedance [13]. By analysing the Lx waveform, it is possible duration, airflow and glottal state. In particular, it is shown to determine for what portion of the glottal cycle the vocal that breathy nasals are typified by an increased duration and a folds are apart, and how firm the contact between the vocal sharp rise in total airflow, culminating in a peak following folds is on contact. The shape of the Lx waveform is also of the release of the nasal stop constriction. ISBN 978-0-9581946-3-1 © 2010 ASSTA Accepted after peer review of full paper 22 14-16 December 2010, Melbourne, Australia use when analysing phonation type, as it is expected to be of repetitions of a single token, was saved individually in a more sinusoidal shape for breathy voice [14]. PCQuirer, and then exported to the Emu Speech Database The greater amount of turbulent airflow expected Management System (Version 2.2.3; [19]; henceforth with breathy voice [12] is a feature that can be measured ‘Emu’). using aerometry. Given a comparable subglottal air pressure, In total, allowing for corrupt recordings and it is expected that breathy voice will allow a greater volume impromptu amendments to the wordlist by the speaker, the of airflow to reach the oral and nasal cavities, and this can be acoustic and articulatory signals of 211 tokens, were measured using airflow masks. This method was also a key in recorded. Segmentation based on the acoustic signal was determining the articulatory correlates of breathy voice in performed using Praat [20] and Emu prior to either acoustic Sumi. It has been demonstrated by Ladefoged [15] and used or articulatory analyses due to a preliminary spectrographic by Bhaskararao and Ladefoged [6] and Blankenship et al. inspection of breathy nasals in Sumi suggesting clearly [16] to identify voiceless nasals in Burmese and Khonoma distinct composite segments to breathy sonorants. Angami, for example - both languages of the same family as The four nasals analysed in this paper were referred Sumi. to as /m/, /n/, /mh/ and /nh/, where the first two of these are modal nasals and the last two are breathy nasals. The 3. Methodology composite segments of the breathy nasals were analysed, and these were referred to as, for example, [m] in /mh/ and [h] in /mh/. After completion of labelling, the acoustic and 3.1. Speakers articulatory data was queried using the Emu-R software The research was carried out in the Phonetics Laboratory at environment [21, 22]. the University of Melbourne. Potential speakers were There was evidence of breathy segments being therefore required to be from the local area, which articulated in modal voice in some tokens. For example, in an consequently limited the number and variety of Sumi isolated speech utterance containing five tokens, breathy speakers available. One female Sumi speaker participated in voice was apparent in all but one token. It was clear from this research. She was aged in the mid-30s and was a spectral analysis that this single token contained a competent speaker of English as a second language. She was prototypical modal nasal, while the remaining four displayed a native Sumi speaker, raised in Nagaland with Sumi- the expected patterning for a breathy nasal. These anomalous speaking parents. The speaker had worked as a language tokens were analysed as modal nasals, which led to an consultant in the past. imbalance in the number of breathy and modal nasal tokens. In a number of utterances where breathy nasal tokens were 3.2. Materials anticipated, none were present in either connected or isolated speech. This was identified by the speaker as an issue with A wordlist was compiled using an English-Sumi dictionary the orthographic representation in the dictionary used for [17] and the grammar and phonetic reader of Sumi, both by compiling the word list. This further led to an uneven number Sreedhar [7, 8]. It was designed to incorporate all phonetic of breathy and modal nasal tokens. environments in which both the breathy and modal nasals existed in contrastive distribution, creating a list of words 4. Results containing these nasals in (at least near) minimal pairs. As Bradley [18] suggests, there is often some Spectrographic analysis showed that the initial, non-breathy correlation between tone and phonation in Tibeto-Burman portion of breathy nasals – that portion equating to, for languages.