- A cross-sectional study on 20 primary schools at Gia Lam district, with a large sample size showed that the rate of voice disorderamong primary school teachers at Gia Lam district was high (87.82%), 70% had 3 symptoms, in which loss of voice from time to time (64%), rapid fatigue accounting for 61.34%, shortness of breath when speaking (57.9%) and hoarse voice (55.8%).