Dysphonia Interference in Schoolteachers' Speech Intelligibility in the Classroom

"Among the most common occupations, schooteachers are the ones who experience the most changes throughout their career. Considering this, the present study aims to verify whether dysphonia in three different degrees may compromise the speech intelligibility of schoolteachers in the classroom.

Overall, 39 students, average age 10 years, randomly selected from a public school in the Federal District, Brazil (Distrito Federal, Brasil) performed a transcription task of 20 sentences spoken by four distinct female voices in a classroom, one with a control voice (normal), another with mild dysphonia, 1 with moderate dysphonia and another with severe dysphonia. None of the voices in the study presented changes, neither in fluency nor articulation nor neurological changes. The sentences were previously recorded in an acoustically treated booth, with a microphone on a pedestal 5 cm away from the speaker's mouth. For each sentence to be recorded, the speech model was provided by the speech therapist and then repeated by the speaker according to the model. Each voice recorded 5 different sentences, phonetically balanced and with equivalent number of words. The students included in the study underwent auditory, auditory processing, sequential memory for verbal sounds and sound source location tests, fulfilling the normality criteria. They also did not have neurological or motor disorders or learning, speech or language disorders. Academic success was also taken into account. For the experiment, a speaker was placed in front of the classroom, 1 m from the wall and 1 m from the floor, and students were randomly assigned to the classroom seats. After listening to each sentence, some time was assigned for its transcription by each student.

The occurrence of errors was higher in voices with moderate and severe dysphonia, in which a significant difference was found (P ≤0.003) showing that voices with moderate and severe dysphonia were less intelligible than the normal voice (control voice). No difference was found between the normal voice and the mild dysphonic voice. Binary logistic regression analysis also showed that students had a 2.55 times higher chance of making mistakes with moderate dysphonic voice (P ≤0.011), and that this chance was 3.06 times greater for severe dysphonic voice (P ≤0.002) when compared to the normal voice (control voice).

Moderate and severe dysphonia in the voices of schoolteachers interferes with the intelligibility of students, and the greater the degree of dysphonia of the teacher, the greater the chance that the student will make intelligibility errors."