SPECTRAL-ANALYSIS OF TARGET-APPROPRIATE T AND K PRODUCED BY PHONOLOGICALLY DISORDERED AND NORMALLY ARTICULATING CHILDREN

Previous research (Forrest, Weismer, Hodge, Dinnsen and Elbert, 1990) has shown that some phonologically disordered children differentially mark seemingly homophonous phonemes; however, the resulting contrast m ay be spectrally distinct from that produced by normally articulating children of the same age. In the present investigation possible source s for these differences between normally articulating and phonlogicall y disordered children's productions of target-appropriate phonemes wer e pursued. Spectral characteristics of seemingly correct productions o f /t/ and /k/ in world-initial position were analysed for four normall y articulating and seven phonologically disordered children to assess the effect of recency of acquisition, depth of knowledge of the contra st and/or the effect of a phonological disorder on accuracy and variab ility of production. Results revealed that children who had acquired t he velar-alveolar contrast more recently, and who had incomplete knowl edge of that contrast, produced target-appropriate /t/ and /k/ differe ntly from their normally articulating peers and other phonologically d isordered children with greater knowledge of the Further, the contrast . Further, the phonologically disordered children with greater knowled ge of contrast. Further, the phonologically disordered children with i ncomplete knowledge of the velar-alveolar contrast were less variable than the other phonologically disordered or normally articulating chil dren in the spectral characteristics across repeated productions. Anal ysis of the spectral characteristics of word-initial /t/ and /k/ at a later point in time indicated similarities between all speaker groups in the spectral parameters that distinguished the velar from the alveo lar stop. However, the stability of these parameters across repeated p roductions decreased for the phonologically disordered children with g reater knowledge of the contrast. These effects are related to motor s kill development and found to be consistent with previously demonstrat ed patterns of skill acquisition.