Pre-fortis clipping

One of the most important points to take into account if we want to pronounce vowels correctly is their length. We know that there are long vowels, which in phonetics are marked by a colon after the corresponding symbol (/ɑː/, /ɜː/, /ɔː/, etc.), and short vowels (/ɪ/, /ʊ/, /ə/, etc.). And we should also remember that the phoneme /æ/ has a sort of special status because, even though it’s included in the short vowel group, it’s the longest of the short ones. However, as is often the case in English, that’s not all there is to know. We have to learn about a phenomenon called pre-fortis clipping which changes these notions quite a lot.

The pre-fortis clipping process arises from the fact that the length of a vowel is strongly determined by the voicing of the consonant that  comes after it (or by the absence of any consonant, if this is the case). The term  fortis  is equivalent to voiceless  and clipping  stands for shortening. So, what this convoluted expression means is that when a stressed vowel is followed by a voiceless consonant within the same syllable, the length of that vowel is considerably reduced. This is especially noticeable in the case of long vowels, which are shortened up to half their length.

Listen to some examples and note how clearly this difference can be seen:


Long vowels


Long vowel followed by voiced consonant or pause                                                                             Long vowel followed by voiceless consonant

sound_loud_speaker churn   /ʧɜːn/                                                                                                                                                              sound_loud_speaker church   ɜːʧ/

sound_loud_speaker war     /wɔː/                                                                                                                                                                 sound_loud_speaker warp     /wɔːp/

sound_loud_speaker cheese    /ʧz/                                                                                                                                                            sound_loud_speaker cheat     t/

sound_loud_speaker read       /rd/                                                                                                                                                              sound_loud_speaker reach    /riːʧ/

sound_loud_speaker word     /wɜːd/                                                                                                                                                            sound_loud_speaker work     /wɜːk/

sound_loud_speaker leave     /lv/                                                                                                                                                                sound_loud_speaker lea       /lf/

sound_loud_speaker hard     /hɑːd/                                                                                                                                                              sound_loud_speaker heart    /hɑːt/

sound_loud_speaker wee      /w/                                                                                                                                                                  sound_loud_speaker week     /wk/

sound_loud_speaker bawl    /bɔːl/                                                                                                                                                                 sound_loud_speaker bought /bɔːt/


As you can see, vowels followed by a voiced consonant or a pause keep their normal length, whereas those coming before a voiceless consonant become much shorter.




This process applies to diphthongs as well:


Diphthong followed by voiced consonant or pause                                                                                Diphthong followed by voicelss consonant

sound_loud_speaker rise   /rz/                                                                                                                                                                     sound_loud_speaker rice   /rs

sound_loud_speaker play   /pl/                                                                                                                                                                    sound_loud_speaker plate  /plt/

sound_loud_speaker know   /nəʊ/                                                                                                                                                                 sound_loud_speaker note   /nəʊt/

sound_loud_speaker bow   /b/                                                                                                                                                                    sound_loud_speaker bout   /bt/

sound_loud_speaker employ   /emˈplɔɪ/                                                                                                                                                    sound_loud_speaker exploit   /eksˈplɔɪt/

sound_loud_speaker coal   /kəʊl/                                                                                                                                                                   sound_loud_speaker coat   /kəʊt/

sound_loud_speaker scare   /sk/                                                                                                                                                                sound_loud_speaker scarce   /sks/


Short vowels


Now, let’s see how pre-fortis clipping affects short vowels too, although the difference is not so obvious:


Short vowel followed by voiced consonant or pause                                                                             Short vowel followed by voicelss consonant

sound_loud_speaker man   /mæn/                                                                                                                                                                 sound_loud_speaker map   /mæp/

sound_loud_speaker lag   /læg/                                                                                                                                                                       sound_loud_speaker lack   /læk/

sound_loud_speaker bid   /bɪd/                                                                                                                                                                       sound_loud_speaker bit   /bɪt/

sound_loud_speaker bill   /bɪl/                                                                                                                                                                         sound_loud_speaker bitch   /bɪʧ/

sound_loud_speaker pull   /pʊl/                                                                                                                                                                      sound_loud_speaker pu  /pʊt/

sound_loud_speaker good   /gʊd/                                                                                                                                                                  sound_loud_speaker look   /lʊk/

sound_loud_speaker bum   /bʌm/                                                                                                                                                                  sound_loud_speaker but   /bʌt/

sound_loud_speaker shun   /ʃʌn/                                                                                                                                                                    sound_loud_speaker shu  ʌt/

sound_loud_speaker cod   /kɒd/                                                                                                                                                                     sound_loud_speaker cot   /kɒt/

sound_loud_speaker mob    /mɒb/                                                                                                                                                                 sound_loud_speaker mock  /mɒk/


Consonant clusters


Another interesting fact to remember is that, whenever more than one consonant follow the vowel, the clipping also occurs provided that there is a voiceless one within the same syllable .


Vowel followed by more than one consonant                                                                                            Vowel followed by more than one consonant

sound_loud_speaker lamb   /læm/                                                                                                                                                                 sound_loud_speaker lamp   /læmp/

sound_loud_speaker bend   /bend/                                                                                                                                                               sound_loud_speaker bent   /bent/

sound_loud_speaker hill   /hɪl/                                                                                                                                                                         sound_loud_speaker hilt   /hɪlt/

sound_loud_speaker hell   /hel/                                                                                                                                                                       sound_loud_speaker help   /help/

sound_loud_speaker fell   /fel/                                                                                                                                                                         sound_loud_speaker felt   /felt/

sound_loud_speaker hum   /hʌm/                                                                                                                                                                  sound_loud_speaker hump   /hʌmp/

sound_loud_speaker thin   /θɪn/                                                                                                                                                                     sound_loud_speaker think   /θɪnk/


Nouns and verbs


There are also pairs of verbs and nouns which are actually the same word, the only difference being that the verb ends in a voiced consonant while the noun ends in its voiceless counterpart. This may be reflected in the spelling (devise-device, believe-belief) or not (abuse, house). And here too, in the case of voiceless final consonants (nouns), the preceding vowel is shortened by the pre-fortis clipping phenomenon.


Verbs                                                                                                                                                                                        Nouns

sound_loud_speaker abuse   /əˈbjz/                                                                                                                                                             sound_loud_speaker abuse   /əˈbjs/

sound_loud_speaker house   /hz/                                                                                                                                                                 sound_loud_speaker house   /hs/

sound_loud_speaker devise   /dɪˈvz/                                                                                                                                                           sound_loud_speaker device   /dɪˈvs/

sound_loud_speaker mouth   /mð/                                                                                                                                                              sound_loud_speaker mouth   /mθ/

sound_loud_speaker excuse   /ɪkˈskjz/                                                                                                                                                       sound_loud_speaker excuse   /ɪkˈskjs/

sound_loud_speaker believe   /bɪˈlv/                                                                                                                                                             sound_loud_speaker belief   /bɪˈlf/

sound_loud_speaker use   /jz/                                                                                                                                                                           sound_loud_speaker use   /js/

sound_loud_speaker prove   /prv/                                                                                                                                                                 sound_loud_speaker proof    /prf/


This is the type of work I do with my students in my one-to-one classes. I make them practise these processes with exercises until they improve their comprehension of native speakers and are capable of speaking like that themselves. If you are interested in my classes, you can contact me here.


How important is all this? The shortening of vowels because of a voiceless following consonant is a far more important fact than might seem at first glance. The reason is that it is linked to one of those English features, the devoicing of final consonants, that can make English a devilishly difficult language to understand. Since I’ve already written about it, I’ll just outline it in a nutshell: voiced consonants are normally devoiced when they are in final position and followed by a pause. Consequentely, they sound very much like their voiceless counterparts (/b/ like /p/, /d/ like /t/, etc.).
So, how shall we distinguish hard  from heart  if both d  and t  sound more or less the same, you may well ask? The answer is in the length of the vowel, because although voiced consonants are devoiced the length of the preceding vowel remains intact. So, hard and heart are not distinguished by the final d  or t, as they sound virtually the same, but by the length of the vowel /ɑː/, which is longer in hard because the /d/, even if devoiced here, is in origin a voiced consonant. This is exactly what native speakers do.