Dutch /e/ has the tendency to become /eɪ/ as well (not in Flemish, I think), so /eɪ/ just sounds mostly like "e" to us (Dutch speakers in NL). The "ij" is really /ɛɪ/, but because we don't really have /aɪ/, it turns out that /aɪ/ works fine as a fairly non-ambiguous substitute.
True, but to my ear at least, /eɪ/ is further from /ɛi/ than /aɪ/ is. Maybe more to the point, English speakers (American ones at least) are going to "realize" the name Dijkstra with an /aɪ/ dipthong. "Dayksra" would not occur to us to say.
Phonemes are a funny thing: if an American were to pronounce that last name perfectly (or a Dutch person speaking English, for that matter), other Americans would still hear /daɪkstɹə/, or at most, "/daɪkstɹə/ but it sounds a bit foreign".
Some sounds which we don't produce are audibly not-English-phonemes, like German ü or Scandanavian ø, but others are not. Another example of this is that native English speakers aren't usually sensitive to the difference between the r sound in our word "pear" and the r sound in Spanish "pero", but recognize that "perro" is a different rhotic sound.
> True, but to my ear at least, /eɪ/ is further from /ɛi/ than /aɪ/ is.
If I may ask purely out of curiosity, are you a native English speaker? I only say this because, to my American English ear, [eɪ] and [ɛi] are virtually indistinguishable. Maybe I'm just misunderstanding what you're trying to say....
Does that sound more like "dike" or more like "day"? To me (yes, native American English speaker, of one of the dialects very close to 'Standard'), it is obviously more like the former.
Sorry if I sounded argumentative by the way, that was not my intent at all—it was an entirely honest question, and I'm really bad at wording things (especially via text).... I do agree that the WP recording of "Dijkstra" sounds more like "dike" than "day".
I might've figured out the disconnect. According to this image on Wikipedia[0], the Northern Standard Dutch realization of [ɛi] starts lower than the monophthongal [ɛ] in the same dialect[1]. Just speculation on my part, but maybe in the context of Dutch linguistics, [ɛi] conventionally signifies a wider diphthong than I would've naïvely thought? (If so, I guess this makes me a cautionary tale against directly comparing IPA transcriptions between languages....)
An example from the WP article linked by user BalinKing:
> Some dialects of English make monophthongs from former diphthongs. For instance, Southern American English tends to realize the diphthong /aɪ/ as in eye as a long monophthong [äː], a feature known as /aj/ ungliding or /ay/ ungliding.
You know, where “I spy with my eye” from a (caricatured) Southerner becomes “Ah spah with mah ah”. What are diphthongs in most dialects of English have been turned into monophthongs.
[0] The exceptions being dialects where it monophthongizes to /eː/