Previous acoustic studies of Khmer Language (Henderson 1952, Thomas & Wanna 1987-88, Ratree 1998, Woźnica 2009, Kirby 2014) did not concentrate on the Phnom Penh dialect as the canonical form of Khmer. This study concentrates on the description of standard Khmer vowel distinction in the specific context of the Phnom Penh dialect. Although there is no clear-cut definition of "Standard Khmer", the notion of "speaking clearly" (និយាយច្បាស់/nijiɜj cbah/) may help us to define standard Khmer dialect. This study reports the results of an acoustic-phonetic analysis of the Phnom Penh Khmer dialect. The study finds that all Phnom Penh Khmer vowels presented phonemically and phonetically in the standard Khmer vowel system. Khmer vowels are traditionally separated into two series (a & b) and/or registers (first and second). In Phnom Penh long and short vowels, the first register vowels are lower and more open than the second register vowels. Moreover, the first register vowels are also diphthongized in Phnom Penh, respectively similar to the BB vowels reported by Ratree Wayland (1996). However, the short vowels, for /o/, /ɔ/, /ɑ/ and /a/, are more centralized than the long vowels. Even though in general the Phnom Penh vowel system is a canonical form of the standard Khmer vowel system, some differences exist both in phonology and in phonetics.

{"references": ["Henderson, E.J.A. (1952). The main features of Cambodian pronunciation. Bulletin of the School of Asian Studies, 14, 149-74. 3 plates.", "Kirby, J. (2014). Incipient tonogenesis in Phnom Penh Khmer: Computational studies. Laboratory Phonology, 5(1), pp. 195-230. Retrieved 22 Aug. 2019, from doi:10.1515/lp-2014-0008", "Peter Ladefoged (2001). Vowels and consonants: an introduction to the sounds of languages. Oxford: Blackwell.", "Stevens, Kenneth (2000). Acoustic Phonetics (Current Studies in Linguistics). The MIT Press, New Ed edition.", "Johnson, Keith. (2011). Acoustic and Auditory Phonetics. Hoboken, NJ: Wiley-Blackwell.", "Thomas, D. and Wanna Tienmee. (1987-1988). An acoustic study of Northern Khmer vowels. The Mon-Khmer Studies Journal, 16-17, 99-108.", "Wayland, R. (1998). An acoustic study of Battambang Khmer vowels. The Mon-Khmer Studies Journal, 28, 43-62.", "Wo\u017anica, P. (2009). An Acoustic Study of Khmer Vowel Duration. Investigations Linguistic, XVIII"]}