Year of publication
- 2008 (2) (remove)
- Motor equivalent strategies in the production of /u/ in perturbed speech (2008)
- Several articulatory strategies are available during the production of /u/, all resulting in a similar acoustic output. /u/ has two main constrictions, at the velum and at the lips. A perturbation of either constriction can be compensated at the other one, e.g wider constriction at the velum by more lip protrusion, wider lip opening by more tongue retraction. This study investigates whether speakers use this relation under perturbation. Six speakers were provided with palatal prostheses which were worn for two weeks. Speakers were instructed to make a serious attempt to produce normal speech. Their speech was recorded via EMA and acoustics several times over the adaptation period. Formant values of /u/-productions were measured. Velar constriction width and lip protrusion were estimated. For four speakers a correlation between constriction width and lip protrusion was found. A negative correlation between lip protrusion and F1 or F2 could sometimes be observed, but no correlation occurred between constriction size and either of the formants. The results show that under perturbation speakers use motor equivalent strategies in order to adapt. The correlation between constriction size and lip protrusion is stronger than in studies investigating unperturbed speech. This could be because under perturbation speakers are inclined to try out several strategies in order to reach the acoustic target and the co-variability might thus be greater.
- The use of sensory feedback in the adaptation of perturbed /s/ (2008)
- The study investigates the contribution of tactile and auditory feedback in the adaptation of /s/ towards a palatal prosthesis. Five speakers were recorded via electromagnetic articulography, at first without the prosthesis, then with the prosthesis and auditory feedback masked, and finally with the prosthesis and auditory feedback available. Tongue position, jaw position and acoustic centre of gravity of productions of the sound were measured. The results show that the initial adaptation attempts without auditory feedback are dependent on the prosthesis type and directed towards reaching the original tongue palate contact pattern. Speakers with a prosthesis which retracted the alveolar ridge retracted the tongue. Speakers with a prosthesis which did not change the place of the alveolar ridge did not retract the tongue. All speakers lowered the jaw. In a second adaptation step with auditory feedback available speakers reorganised tongue and jaw movements in order to produce more subtle acoustic characteristics of the sound such as the high amplitude noise which is typical for sibilants.