Many different versions of the standard British English IPA chart exist, with each major dictionary displaying some variation. ‘The Sound of English’ uses a similar set of symbols to the OED (Oxford English Dictionary). You will notice some or all of the following variations in other books and dictionaries:
3. /ɛː/ = /eə/
In GB English the diphthong /eə/ has gradually lost its diphthongal quality and is generally closer to a long mid-open front sound. A similar process is happening to /ɪə/ which may become /ɪː/ in time.
3. /ɛ/ = /e/
English /ɛ/ in BED can be represented as /e/ or /ɛ/, it is generally slightly more open than cardinal vowel [e] and slightly less open than cardinal vowel [ɛ].
4. /a/ = /æ/
The front open sound in BAD has gradually opened in standard pronunciation, making it closer to cardinal [a]. The symbol /æ/ has the disadvantage of appearing to be a diphthong to new learners of English.
5. /əː/ = /ɜː/
In a chart with /ɛː/, it can be highly confusing for learners to also use symbol /ɜː/, though there is no difference in the sound.
16. /ʌɪ/ = /aɪ/
Many speakers start the sounds /aɪ/ and /aʊ/ in different positions, so it can be confusing for learners to have the same symbol in both, using /ʌɪ/ resolves this.