The dependent vowels are listed below, in conventional form with a dotted circle as a dummy consonant symbol, and in combination with the a-series letter "’â". The IPA values given are representative of dialects from the northwest and central plains regions, specifically from the Battambang area, upon which Standard Khmer is based. Vowel pronunciation varies widely in other dialects such as Northern Khmer, where diphthongs are leveled, and Western Khmer, in which breathy voice and modal voice phonations are still contrastive.