• As the degree of judged hoarseness increases, the noise component appears to a greater degree and replaces the harmonic structure in the spectrogram. The relationship between these two components has been quantified as the harmonics to noise (H/N) ratio. The computation is straightforward; 50 consecutive pitch periods of a sustained vowel /a/ are averaged; H is the energy of the average waveform, while N is the mean energy of the differences between the individual periods and the average waveform. Therefore, the H/N ratio could be measured in the clinic with the aid of a small, inexpensive computer. This H/N ratio was successfully applied for evaluating the effectiveness of the treatments for hoarseness. Although the H/N ratio does not aid in making a diagnosis of laryngeal abnormality, it would be an important tool for assessing hoarseness.
(Arch Otolaryngol 1983;109:48-52)
Yumoto E. The Quantitative Evaluation of Hoarseness: A New Harmonics to Noise Ratio Method. Arch Otolaryngol. 1983;109(1):48–52. doi:10.1001/archotol.1983.00800150052010
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