An Introduction to French Pronunciation

12.6 Rule 4
Vowel Length 91
Other vowels, i.e. /i/, /ε/, /a/, /y/, /œ/, /u/ and /b/, are long
when stressed and in a closed syllable ending in /v/, /z/, /ʒ/,
/r/ or /vr/, e.g. (in stressed contexts) rive /ri:v/, les assises
/lez asi:z/, noblesse oblige /nbblεs bbli:ʒ/, partir /parti:r/,
ivre /i:vr/, brève /brε:v/, à l’aise /a lε:z/, que sais-je? /kc
sε:ʒ/, fièvre /fjε:vr/, cave /ka:v/, image /ima:ʒ/, rare
/ra:r/, cadavre /kada:vr/, étuve /ety:v/, il refuse /il rcfy:z/,
refuge /rcfy:ʒ/, impur /hpy:r/, bonheur /bbnœ:r/, veuve
/vœ:v/, œuvre /œ:vr/, je trouve /ʒc tru:v/, il bouge /il
bu:ʒ/, j’ouvre /ʒu:vr/, Limoges /limb:ʒ/, sort /sb:r/, Hanovre
/anb:vr/.
Notes: (i) The ‘lengthening consonants’ /v/, /z/, /ʒ/ and /r/
are all voiced fricatives. (ii) Clusters of two voiced fricatives
other than /vr/ do not cause lengthening, e.g. larve /larv/,
conserve /kfsεrv/, berge /bεrʒ/, large /larʒ/, Panurge
/panyrʒ/, forge /fbrʒ/, quatorze /katbrz/. (iii) The vowel /e/
does not occur in closed syllables (see 10.6.2). (iv) The vowel
/c/ is never stressed (see 11.1.2 (ii)).
12.7 Rule 5
In other stressed closed syllables, the vowels /i/, /ε/, /a/, /y/,
/œ/, /u/ and /b/ are short (but see 12.8), e.g. vide /vid/, vite
/vit/, vitre /vitr/, cime /sim/, signe /si/, filtre /filtr/, (ils)
finissent /finis/, riche /riʃ/, laide /lεd/, pêche /pεʃ/, cercle
/sεrkl/, svelte /svεlt/, auberge /obεrʒ/, parade /parad/, platane
/platan/, montagne /mfta/, vaste /vast/, (ils) partent
/part/, Chartres /ʃartr/, tube /tyb/, costume /kbstym/, urge
/yrʒ/, club /klœb/, bœuf /bœf/, seul /sœl/, jeune /ʒœn/, foule
/ful/, boom /bum/, (il) tousse /tus/, farouche /faruʃ/, boucle
/bukl/, féroce /ferbs/, orge /brʒ/, code /kbd/, globe /g1bb/,
torse /tbrs/, porte /pbrt/.