The turbulent noise ratio: an estimation of noise power of the breathy voice using PARCOR analysis.

The degree of turbulent noise in the breathy voice of 25 patients with incomplete glottal closure was determined by PARCOR (PARtial autoCORrelation) analysis. From 10,000 acoustic data points, 44 PARCOR coefficients were calculated to form the residue wave which is representative of the glottal source. The power difference between the residue wave and the original acoustic wave was calculated in order to define a new measurement of acoustic power termed the turbulent noise ratio (TNR). The 25 patients were studied before and after Isshiki thyroplasty type I (IttI). The TNR became smaller in 24 of these patients following IttI, and corresponded closely with acoustic (Fukazawa's Br-Index), aerodynamic (Isshiki's AC/DC ratio), mean airflow rate during phonation, and videolaryngostroboscopic findings. Data affirm that the TNR accurately reflects the degree of turbulent noise at the glottal source.