Sound change in 19th century RP: TRAP

Seven speakers of RP born in the latter half of the 19th century are examined for signs of a reported sound change to TRAP. They are described here.

RP TRAP was formerly close to DRESS at IPA [æ] (accompanied by compression of DRESS and KIT towards FLEECE), but is now an open [ae] (with DRESS and KIT spread out). This change was not reported for RP by Jones (1932) or Gimson (1962) (although Gimson recognised it as regional Southern). The change in RP was reported relatively recently (Wells 1982, Bauer 1985, Detterding 1997), although it can be seen in Wells’ data (1962). Fabricius (2007) found that this change was already in progress in the early decades of the 20th century, her oldest example born in 1900.

Bauer, Laurie. 1985. Tracing phonetic change in the received pronunciation of British English. Journal of Phonetics 13:61-81.
Deterding, David. 1997. The formants of monophthong vowels in Standard Southern British Pronunciation. Journal of the International Phonetic Association 27:47-55.
Fabricius, Anne H. 2007. Variation and change in the TRAP and STRUT vowels of RP: a real time comparison of five acoustic data sets. Journal of the International Phonetic Association 37:293-320.
Gimson, A. C. 1962. An Introduction to the Pronunciation of English. London, Arnold.
Jones, Daniel. 1932. An Outline of English Phonetics. Leipzig: Teubner. 3rd revised edition.
Wells, J. C. 1962. A Study of the Formants of the Pure Vowels of British English. MA thesis, University of London.

All the recordings have been subjected to lossy MP3 compression at some time during their lives. They were analysed using Praat, by LPC formant tracking where possible, by measuring directly on the spectrogram where that failed, or by measuring formant peaks on FFT slices. Some lower back vowels had to be abandoned and there are consequently fewer instances of FOOT, THOUGHT or LOT in some cases. Vowel formant frequencies were collected from fully focused syllables, to minimize spectral variation due to vowel reduction. Vowels were sampled at the moment where vowel articulation was least affected by surrounding consonant articulations, selected by comparing VC and CV formant transitions, to minimize spectral variation due to coarticulation.

Figure 1. F1/F2 diagram for RP12 Robert Baden-Powell.
Figure 2. F1/F2 diagram for RP06 Stanley Baldwin.

Figure 3: F1/F2 diagram for RP13 Neville Chamberlain

Figure 4. F1/F2 diagram for RP08 Sir Richard Paget, based
on data in his Human Speech, 1930, London, Kegan Paul
(formants reported as frequency ranges).

Figure 5. F1/F2 diagram for RP01 W. Somerset Maugham.
Figure 6. F1/F2 diagram for RP07 Daniel Jones, combined
from an educational recording (1929) and the commentary
to the 1956 cardinal vowel recording

Figure 7. F1/F2 diagram for RP02 Harold MacMillan.

Tongue height is interpreted as F1 on the vowel diagrams, tongue backing as F2 (explained here). Some of these examples had shorter than average vocal tracts with F2 reaching or approaching 2500Hz in FLEECE, and F1 extending beyond 800Hz. Most were spoken energetically with larger mouth openings so that F1 extended to 700-800Hz. An exception was Neville Chamberlain (Figure 3), whose F1 rarely reached 700Hz (except for BATH).

Open vowels are produced with a low pharyngeal constriction, with F1 higher than about 600-650Hz for most men, and higher for women and children (explained here). Neville Chamberlain’s open vowel limit was lowered to at least 550Hz, presumably due to his less energetic articulation.


Only Neville Chamberlain (Figure 3) had the earlier closer TRAP along with compression of DRESS and KIT towards FLEECE. His F1 centre of gravity for TRAP was about 500-600Hz, where the other examples had their DRESS zone. And yet he also had occasional instances of open TRAP with F1>600Hz.

Additionally, W. Somerset Maugham and Harold MacMillan (Figures 4, 7) had their open TRAP zones very close to DRESS but without compressing DRESS and KIT.

All the others had open TRAP with F1 at 650-800Hz, indicating that this sound change was already in progress by the 1850s.

The open [æ]-like timbre is produced with a maximally wide low pharyngeal constriction (cross section in the constriction > and a large mouth opening, yielding F1>600Hz and F2>1600Hz. A smaller mouth opening for a close TRAP lowers its F1 towards 500Hz, compromising DRESS and leading to the compression of DRESS and KIT towards FLEECE. The sound change meant that new generations no longer had smaller mouth openings for TRAP, thereby limiting F1>600HZ. This demonstrates there is one [æ]-like zone that can be reached from a maximally wide low pharyngeal constriction. Smaller mouth openings add a hint of [ɛ] to the timbre, yielding the closer IPA [æ], while larger mouth openings limit F1, yielding open [æ]. This is why Neville Chamberlain could produce the closer IPA [æ] most of the time, but occasionally also had instances of open [æ].

Listen to closer and open TRAP (400-700Hz) by Neville Chamberlain, arranged from high F1 to low F1 from open [æ] to close [æ] (Figure 3):
“factories plans bad attack ambassador handed practice cabinet man plans”

Listen to open TRAP close to DRESS (F1 590-690Hz) by Somerset Maugham (Figure 5):
(“happened characters fact back pattern gathered”)

Listen to open TRAP close to DRESS (F1 600-660Hz) by Harold MacMillan (Figure 7):
Africa Africa Africa travel”

Listen to open TRAP (650-800Hz) by Robert Baden-Powell (Figure 1):
“that carry travelling had happiness that happiness glad happy”

Listen to open TRAP (600-800Hz) by Stanley Baldwin (Figure 2):
“national crash stands tax balance”

Listen to open TRAP (600-800Hz) by Daniel Jones (Figure 6):
“back stand handling dashing gangways”

In conclusion, picking seven RP speakers at random, born in the second half of the 19th century, reveals that the TRAP change was apparently already in progress. This particular sample included just one clear example with the earlier close TRAP, with DRESS and KIT compressed towards FLEECE, and yet even he had a mix of close and open TRAP. This is a remarkable and presumably controversial result, with no explanation for how could have been missed for so long. One possible reason is that Jones never expected an open vowel more front than cardinal 4, while open [æ] is indeed more front than that (explained here).