The aim of the study was to establish whether /u/-fronting, a sound change in progress in standard southern British, could be linked synchronically to the fronting effects of a preceding anterior consonant both in speech production and speech perception. For the production study, which consisted of acoustic analyses of isolated monosyllables produced by two different age groups, it was shown for younger speakers that /u/ was phonetically fronted and that the coarticulatory influence of consonants on /u/ was less than in older speakers. For the perception study, responses were elicited from the same subjects to two minimal word-pair continua that differed in the direction of the consonants' coarticulatory fronting effects on /u/. Consistent with their speech production, young listeners' /u/ category boundary was shifted toward /i/ and they compensated perceptually less for the fronting effects of the consonants on /u/ than older listeners. The findings support Ohala's model in which certain sound changes can be linked to the listener's failure to compensate for coarticulation. The results are also shown to be consistent with episodic models of speech perception in which phonological frequency effects bring about a realignment of the variants of a phonological category in speech production and perception.

This paper presents a longitudinal analysis of the extent to which age affects F 0 and formant frequencies. Five speakers at two time intervals showed a clear effect for F 0 and F 1 but no systematic effects for F 2 or F 3 . In two speakers for which recordings were available in successive years over a 50 year period, results showed with increasing age a decrease in both F 0 and F 1 for a female speaker and a Vshaped pattern, i.e. a decrease followed by an increase in both F 0 and F 1 for a male speaker. This analysis also provided strong evidence that F 1 approximately tracked F 0 across the years: i.e., the rate of change of (the logarithm of) F 0 and F 1 were generally the same. We then also tested that the changes in F 1 were not an acoustic artifact of changing F 0 . Perception experiments with the main aim of assessing whether changes in F 1 contributed to age judgments beyond those from F 0 showed that the contribution of F 1 was inconsistent and negligible. The general conclusion is that age-related changes in F 1 may be compensatory to offset a physiologically induced decline in F 0 and thereby maintain a relatively constant auditory distance between F 0 and F 1 .

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The present study is concerned with lax /u/-fronting in Standard British English and in particular with whether this sound change in progress can be attributed to a waning of the perceptual compensation for the coarticulatory effects of context. Younger and older speakers produced various monosyllables in which /u/ occurred in different symmetrical consonantal contexts. The same speakers participated in a forced-choice perception experiment in which they categorized a synthetic /I-u/ continuum embedded in fronting /s_t/ and non-fronting /w_l/ contexts. /u/ was shown to be fronted for the younger age group in both production and perception. Although there was no conclusive evidence that younger listeners compensated less for coarticulation than did older listeners, the size of the coarticulatory influence of consonantal context on /u/ in perception was found to be smaller than in production for the younger than for the older group. The findings are consistent with a model of sound change in which the perceptual compensation for coarticulation wanes ahead of changes that take place to coarticulatory relationships in speech production. As a result, the perception and production of coarticulation may be unusually misaligned with respect to each other for some speaker-listeners participating in a sound change in progress.

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