The efficacy of a voice training program: a case-control study in China.

The objective of this study was to design a voice training program for Chinese speakers, and to evaluate its efficacy. It was a prospective, randomized, case-control study practiced in three middle schools in Beijing, China. Teachers in the treatment group received voice training for 4 weeks, whereas the control group subjects received no treatment. The voice training program, which was adapted for Chinese, contained vocal hygiene education and group voice training. The outcome was assessed by voice handicap index (VHI), maximum phonation time (MPT) and acoustic analysis parameters including, noise to harmonic ratio (NHR), jitter and shimmer. The results showed that at the onset of the study, no significant differences were found between the subjects in two groups for VHI, MPT and NHR. VHI of treatment group subjects who received voice training decreased significantly, whereas VHI of control group subjects showed no significant change. Treatment group MPT was significantly increased after training, whereas the control group one presented no significant change during the same period. NHR in treatment group decreased significantly after training, whereas the one in control group showed no significant change. There were no significant changes for jitter and shimmer in both groups before and after the study. So we conclude that the voice training program is suitable to treat voice diseases, particularly for middle school teachers. This result provided reliable evidence for carrying out further voice training in China.