A new index for evaluation of the turbulent noise in pathological voice.

The validity of the parameter Br index, which was designed as an indicator of the turbulent noise in breathy voice, was tested. The parameter was determined by the ratio between energy of the second derivative of the high-pass filtered wave and that of the nonderived high-pass filtered wave. The principle of this method is the utilization of the difference in the frequency range between the turbulent noise and other components present. The parameter was found to correlate with the perception of breathiness. Clinical applications of this index suggest the possibility of using it further as a detection tool for diseases that generate turbulent noises.