An Introduction to French Pronunciation

The Vowels in Detail 55
to attempt to produce some kind of substitute for /y/ by
beginning with a front unrounded vowel ([i]) and continuing
with a back rounded one ([u]), i.e. something like [liun]
(or [liwn]) for /lyn/; this may or may not be intelligible to a
French-speaker but, at best, will mark the speaker out as
having a strong foreign accent.
For the alternation between /y/ and /d/, see 13.7.
10.4 /u/ – High Back Rounded
The main point for English-speakers to note is that, for French
/u/, the lips are clearly and firmly (not, as in English, loosely)
protruded and rounded.
English-speakers from areas (e.g. parts of Lancashire and
central Scotland – but see below) where the oo of too, cool,
etc., is centralized (i.e. pronounced further forward in the
mouth than in other varieties of English) should take particular
care to pronounce /u/ well back in the mouth; there is all
the more need to stress this point since there seems to be a
growing tendency on the part of speakers from many parts of
England to bring the vowel somewhat forward, though not as
much so as in the areas mentioned above.
It should also be noted that many English-speakers start
rounding their lips some time after beginning to pronounce
the vowel of too, cool, food, loo, etc., thereby producing something
like [tcu, kcul, fcud, lcu]. In French, on the other hand,
in words such as tout, coup, loup, etc., the lips are rounded,
and firmly so, even before the consonant is pronounced.
/u/ is nearly always written ou or oû, e.g. loup /lu/, foule
/ful/, ouvre /u:vr/, goût /gu/. Note, however, the words où
/u/, août /u/ or /ut/, and saoûl /su/ (and its derivatives).
For the alternation between /u / and /w/, see 13.7.