[Harmonic/noise ratio and spectrographic analysis in vocal abuse pathology]

Vocal abuse lesions disturb voice production by increasing the presence of noise in the voice. The harmonic-to-noise ratio (H/N) and spectrography are two different ways to evaluate noise components in the voice. A study was made of 52 patients (32 polyps, 11 Reinke's edema and 9 nodules) who underwent microlaryngeal phonosurgery. The grade of glottic closure was determined by stroboscopy; H/N and the long-term average spectrum (LTAS) at low-frequency (0-2000 Hz) were measured with a CSL-4300 instrument. Stroboscopy and acoustic analysis were made before surgery and two week and one month after surgery. Before surgery, the LTAS revealed weak harmonics, as shown by H/N values. After surgery, H/N values and harmonic energy increased. Preoperative and postoperative differences were significant (p < 0.05). Improved glottic closure after surgery improved the acoustic parameters.