Contrast and covert contrast in the speech production of children.

Abstract

Background: Speech acoustics.

Aim: To acoustically analyze the substitution between /t/ and /k/ in the speech production of children with typical and deviant acquisition process in order to identify and quantify the presence of covert contrast.

Method: The experiment involved the repetition of words that combined /t/ and /k/ with /a/ and /u/ in stressed position. Participants were 9 children divided in three groups: children in the acquisition process of the phonological contrast (G1); children with phonological disorder (G2); and children with typical productions (G3). The speech productions were analyzed and edited using software Praat. The acoustic parameters adopted were: burst spectral characteristics; CV transition and durational characteristics. Duration parameters were analyzed by Friedman ANOVA while the other parameters were analyzed using two-way ANOVA and Hierarchical Linear Modeling. The adopted statistical significance level was of 0.05.

Results: Acoustic analysis indicated the presence of covert contrast in the productions of children in G1 and G2 (80% and 57.14% of substitutions respectively). In addition, acoustic analysis revealed differences in how well the children differentiated the two occlusives and which acoustic parameters were used to differentiate them.

Conclusion: A lot of the substitutions presented in the speech of children in typical and deviant acquisition process are in fact covert contrasts. Moreover, the acoustic analyses allowed the detection of differences in the fine phonetic detail of children's speech production.