Acoustic analysis of voice: Iranian teachers

In Iran, the total number of elementary schoolteachers is estimated to be nearly 300 000 people and this population is at risk for developing voice disorders. Acoustical characteristics of voice for schoolteachers in Iran are unknown but are relevant to the quantitative description, diagnosis, intervention, reassessment, and outcomes of their voices.

Fifteen female and 15 male Iranian primary schoolteachers in the age range of 35-40 years with 15 years teaching experience volunteered to participate in the study. The control group consisted of 30 Iranian adults aged 35-40 years (15 men and 15 women). Recordings and audio signal analyses were carried out using Praat software. Each subject was asked to sustain the vowel /â/ using habitual and constant vocal pitch, loudness, and quality for at least 5 seconds. Five tokens from each subject were obtained.

For the male subjects, the results indicated no significant difference (at the 0.05 level) for each variable between the two groups. However, for the female subjects, t tests showed significant differences between the teachers and the nonteacher controls in all parameters at the 0.01 level. The Iranian female teachers had significantly lower F(0) (190.27 Hz) than the control group (236.32 Hz). Also, for the perturbation acoustic parameters (jitter% and shimmer%), the female teacher group had significantly higher values than their corresponding control group. Similarly, the harmonics-to-noise ratio (HNR) measures for the Iranian female teacher population were significantly lower than for their corresponding control group.

The results indicate that female Iranian teachers appear to be more susceptible to voice stability change than the male Iranian teachers. Also, acoustic analysis of voice for teachers may significantly contribute to the objective voice examination of this group. Further investigations of factors that promote individual susceptibility to vocal stability are necessary.