Computer analysis of hoarseness
Hidetsugu Kojima, Wilbur James Gould, Anthony Lambiase · The Journal of the Acoustical Society of America · 1979
A spectrogram of a normal sustained vowel, taken with a narrow filter, shows well developed harmonics as equally spaced horizontal stripes, while that of a hoarse voice presents noise components as a cloudy shadow between the harmonics. Harmonic components are replaced by noise components as the degree of hoarseness becomes more severe. If the acoustic energy of the harmonics is calculated separately from that of the noise components, the degree of hoarseness can be determined as a ratio of harmonics versus noise, or the signal-to-noise ratio. The harmonic components in a hoarse voice were separated from the noise components using a small laboratory computer. The ratio of the signal-to-noise was calculated and compared to the auditory impression for 58 subjects. The calculated results showed a positive correlation to the auditory impression, and it was suggested that this would be a useful method for the quantitative evaluation of hoarseness.