The TRAP vowel

The trap vowel varies along the front–back and open–close dimensions and is variously transcribed as [a æ ε]. What cannot be shown from the vowel quadrilateral so easily is the differences in duration. In the USA, this vowel is regularly long in duration in comparison with other varieties of English.

The symbol [æ] stands for three different qualities: most open in Australia, closest and frontest in RP and most central in American English. If we wanted to distinguish these qualities while using the same symbol, we could elaborate the transcriptions with diacritics. ‘Closer’ and ‘more open’ are handled with  respectively; ‘fronter’ and ‘backer’ with [+], [-]. Vowels shifted to the centre of the quadrilateral can be marked with  . So we could write  for RP,  for Australian and [æ] for American. This transcription style is comparative. Another strategy would be to refer the qualities directly to CVs, in which case we might transcribe RP as  (i.e. more open than CV3, [ε]), Australian as [a] (close to CV4) and American as [ä] (more centralized than CV4, [a]). This transcription style is more impressionistic. It is precisely because of the problems of deciding which symbol to use that phoneticians use graphs to plot where vowels lie, even if this is just an approximation.