Collective spectral pattern complexity analysis of voicing in normal males and larynx cancer patients following radiotherapy

Normal male voicing is defined, and voicing recovery after radiotherapy for larynx cancer quantified, using spectral domain complexity analysis of electro-glottogram conductance variations measured across the larynx during vowel phonation. These variations directly correlate with vocal fold vibrations that drive voice production. Approximate entropy is shown to concisely quantify the collective spectral pattern of the sustained impedance waveform after normalisation with respect to the varying fundamental frequency and power. It reveals a double banded reference standard in normal males. Forty-eight male larynx cancer patients were studied in parallel with an unrestricted perceptual analysis before and 1 year after radiotherapy. Two-thirds of patients had spectral approximate entropy values close to normal approximate entropy reference standards after 1 year. A quarter of patients showed reduced approximate entropy, predominantly in the most aberrant perceptual categories. Collective spectral pattern complexity analysis of vowel phonation has the potential to be a reliable, single parameter measure of voicing quality in these cancer patients.