Glottal Stops Of Patients With Cleft Palate:a Preliminary Acoustic Study

Articulation disorder is quite an important factor that seriously influences the speech of patients with cleft palate after the palatal operations. Glottal stop is one of the compensatory articulations in cleft palate speakers. Clinicians always find it is difficult to identify the glottal stops correctly.So I observed the acoustic characteristics of glottal stops produced by patients with cleft palate and compared them with the normal peers, trying to provide some evidences for clinical diagnosing and treatment.Twenty patients with cleft palate, ranging in age from 3 years old to 8 years old (5.5 years old in average), were chosen from those who coming to the department of cleft lip and palate of the West China Hospital of Stomatology for their first surgery during the period from July in 2004 to April in 2005. They were judged to be glottal-stop-producers by two speech pathologists. The normal peers, ranging in age from 4 years old to 10 years old (6.5 years old in average), were selected from those who coming to the department of dentistry of the West China Hospital of Stomatology during the same period of time. These were judged to be absolutely normal speakers bythe same two speech pathologists. In their own way, all the children were asked to produce following sounds: /ciau/ /pai/ /t'u/; /s(?)/ /k'r/ /p'u/ /t'au/; /tA//ku/; /i/ /k'au/ /tci/ /suan/. Then the speech spectroanalysis and the comparisonwere performed by one investigator.Complex results were found. The acoustic characteristics of glottal stops change a lot when they substitute or accompany with different oral stops. 1 .the emergence of spikes: (1) no spike is found where it should be; (2) an abnormal spike exists in unexpected place; (3) more spikes appear when there is a double articulation. 2.changes of voice onset time: (1) obviously shortened when a glottal stop substitutes an oral stop; (2) when a glottal stop goes with an oral one, the time maybe normal or prolonged. 3. The formant transitions of the patients are quite different from those of the normal peers: the changed locus rises to a level above 3000Hz. 4.spetroanalysis of spikes: the central frequency and the lowest frequency of the concentrated frequency area decrease; heavier energy and new concentrated frequency area appear at a lower frequency level.Above all, we found the acoustic changes of glottal stops are very complicated. We have to consider in every single aspects of acoustic analysis to identify it.