Sound change in 19th century RP: MOUTH

Seven speakers of RP born in the latter half of the 19th century are examined for signs of any sound changes in RP MOUTH. They are described here. Data is presented for five of the seven informants (there was no information on Richard Paget’s diphthongs, while Somerset Maugham’s sample was too short to include any). MOUTH is fairly infrequent in running speech and there are consequently few instances for some of the speakers.

Jones (1932) described RP MOUTH as [au], starting at cardinal 4 or further back. He warned against starting the diphthong at [æ] as this was dialectal, especially London. Gimson (1962), and Wells (1982) reported a growing tendency to start the diphthong nearer [ɑ], to increase the distance to the regional pronunciation. Jones also noted that it was sufficient to proceed only part of the way towards [u], for example [ao] was adequate. In consequence of both observations, Gimson preferred to transcribe this dipthong as [ɑʊ].

Gimson, A. C. 1962. An Introduction to the Pronunciation of English. London, Arnold.
Jones, Daniel. 1932. An Outline of English Phonetics. Leipzig, Teubner. 3rd edition.
Wells, J. C. 1982. Accents of English. Cambridge, CUP. Vol. 2.

Jones’ and Gimson’s warning is understandable. The pronunciation of this diphthong in most rural areas round London in the 1850s was still [ɛu] (Ellis 1885), and Gimson suggested this was still so in the 1960s. The popular London pronunciation was spreading eastwards to industrial towns along the Thames in Kent and Essex in the 19th century, and thence to neighbouring areas and eventually, by the 20th century, to the rest of the home counties (Wood 2017, and here). These regional pronunciations were stigmatized until the 1960s or 1970s, and MOUTH was, and still is, a reliable criterion for distinguishing RP from regional home counties or London SBE.

Ellis, Alexander. 1889. On Early English Prununciation. Teubner, Vol 5.
Wood, Sidney. 2017. A spectrographic study of sound change in nineteenth century Kent. In Tsudzuki, Masaki & Masaki Taniguchi (eds), A Festschrift for Jack Windsor Lewis on the occasion of his 90th Birthday, 215-246, Journal of the English Phonetic Society of Japan 21.

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 MOUTH by Robert Baden-Powell

Figure 2. F1/F2 diagram for MOUTH by Stanley Baldwin

Figure 3. F1/F2 diagram for MOUTH by Neville Chamberlain

Figure 4. F1/F2 diagram for MOUTH by Daniel Jones

Figure 5. F1/F2 diagram for MOUTH by Harold MacMillan


Two of these examples illustrate the frontish start for the diphthong, with F2 around 1500Hz – Robert Baden Powell (Figure 1) and Neville Chamberlain (Figure 3) as described by Jones. The others have F2 around 1250Hz. None of them start the diphthong with regional SBE [æ].

There was considerable variation in the ending, foreseen in Jones’ and Gimson’s descriptions with expected endings [u-ʊ-o]. In fact there were endings as open as [ɔ] with F1 higher than 600Hz or more. The closest endings, [u]-like with final F1 below 400Hz., were by Neville Chamberlain and Daniel Jones (Figures 3-4). Robert Baden Powell and Harold MacMillan (Figures 1, 5) had the full range [ʊ-ɔ] with F1 ending at 400-600Hz. Stanley Baldwin’s MOUTH (Figure 2) all ended at [ɔ].

To produce this diphthong, the start requires a low pharyngeal constriction and a large mouth opening with spread lips. The dynamic movement towards the [u]-like ending requires a tongue body gesture towards the soft palate, closing of the mouth (mandible raising) and gradual lip rounding. Undershoot ([ʊ o ɔ] etc) occurs if the dynamic part is broken off before completion.

Listen to the [au]-like MOUTH by Daniel Jones (Figure 4):
“found found”

Listen to the [au]-like MOUTH by Neville Chamberlain (Figure 3):
“Downing now announced now profound now

Listen to the [au-aɔ]-like MOUTH by Robert Baden Powell (Figure 1),
ordered by rising final F1 from [au] to [aɔ]:
“scout out scouting scouts without found”

Listen to the [au-aɔ]-like MOUTH by Harold MacMillan (Figure 5),
ordered by rising final F1 from [au] to [aɔ]:
“houses town proud mountains now founded”

Listen to the [aɔ]-like MOUTH by Stanley Baldwin (Figure 2):
pound power doubt down


All of these examples, born in the 19th century, produce MOUTH exactly as Jones and Gimson described it. This is classic RP. The only surprise was the ending as open as [ɔ], with F1 beyond 600Hz, by three of these five.