A method for turbulent noise estimation in voiced signals.
In this article a new acoustic parameter is introduced and it is shown that it may serve as an indicator of laryngeal function. It is termed the turbulent noise index (TNI) and is defined as 100(1 - Rmax), where Rmax is the mean value of the maximum correlation coefficient between each pair of consecutive glottal cycles in the voiced signal. A method for its calculation is described. Experiments with synthetic and natural voice signals show that TNI is almost independent of frequency modulation noise and amplitude modulation noise. TNI is compared with HNR (harmonic-to-noise ratio) and NNE (normalised noise energy) which require high stationarity of the voice signal and are substantially affected by slow changes of frequency and amplitude. When the parameters HNR and NNE are used to discriminate between normal and pathological voices, the overlap area contains 21.5% and 23.5% of the total number of pathological voices, respectively. Using TNI, the normal and pathological voices overlap is 14.8% of the total number of pathological voices, i.e. compared to the other noise parameters TNI has a significant advantage as a diagnostic parameter.