Tayao (2008) noted that the vowel inventory of the acrolectal group resembles closely that of General American although at times the low central vowel /a/ is in free variation with the low front vowel /æ/. Present, too, in the acrolectal variety are stressed /ʌ/ and unstressed schwa /ə/, with the latter or /ɪ/ used in place of destressed vowels in rapid speech. The vowel /æ/ may not be as commonly used in this variety of English, and /ʌ/ is not present in the syllable-initial position in a number of Philippine languages, including Tagalog and Cebuano. Pillai et al. (2010) acoustic analysis supported the findings of Tayao's (2004, 2008) acrolectal description, with the exception of small differences between /i/ and /ɪ/. The tension–lax distinction was mostly maintained, but the distinction between tense and lax vowels was not as clear. This suggests that the quality of the vowel sounds may vary among speakers and that their sociolinguistic background plays a role in determining their vowel quality.
/i/ and /ɪ/
Some speakers may merge or replace the short /ɪ/ phoneme with the longer /i/ phoneme, causing the words "peel" and "pill" to sound similar or identical.
In a study by Berowa and Flores (2020), participants tend to preserve the tenseness of /i/ in words like teacher [tɪtꭍər], fields [fildz], please [pliz], deep [dip], sheep [ꭍip] and feast [fist] in the reading tasks. However, speakers seemed to use its highfront short /ɪ/ counterpart in words like these, believe, nobody, leave, degree and conscientious which were heard as [ðɪz], [bəlɪv], [nobadɪ], [lɪv], [dɪgrɪ] and [kanꭍɪƐnꭍəs] in their spontaneous responses.
/e/ and /Ɛ/
The mid-front vowels /e/ and /ɛ/ in Philippine English are both distinctively tense and lax, respectively (Berowa and Flores, 2020). This distinction is preserved by all speakers, as shown by their pronunciation of words like "age," "days," "gate," "base," and "stayed." The mid-front /e/ vowel is present as a feature of the acrolectal and basilectal varieties of Philippine English. According to previous studies, this vowel is also found in some Philippine languages due to American and Spanish influences. This study confirms the existence of /e/ in the vowel inventory of Philippine English and its connection to these linguistic influences.