Acoustic properties of utterance-initial glottal stop in Hawaiian

The Hawaiian phoneme inventory includes a consonant (ʻokina) typically described as glottal stop. Recent studies have found that ʻokina is rarely produced with full glottal closure utterance-medially, and is instead produced as a period of creaky phonation. This study investigated the acoustic correlates of utterance-initial ʻokina following a pause. Although visible creaky phonation did not occur for utterance-initial ʻokina, several reliable acoustic correlates were found during the first vowels of utterances that started with ʻokina. Vowels preceded by ʻokina had higher fundamental frequency, more abrupt onsets of acoustic energy, greater acoustic energy both in the fundamental frequency and across all frequency ranges, lower harmonics-to-noise ratios, and higher jitter than vowels that started without a preceding ʻokina. Linear discriminant analyses of the data showed that these acoustic correlates were able to correctly categorize ∼75% of productions. Although no concurrent articulatory data were collected, arguments are provided to suggest that ʻokina is regularly produced as full glottal closure utterance-initially in Hawaiian, possibly because of effects of prosodic strengthening. We believe the present study is the first to establish a relationship between utterance-initial glottal stop and these acoustic effects on the following vowel.