A physiological basis for two group, healthy male voicing identified using spectral approximate entropy

December 13-15, 2007: Firenze, Italy, ed. by C. Manfredi, ISBN 978 88-8453-673-3 (print) ISBN 978-88-8453-674-7 (online) © Firenze university press, 2007. Abstract: The approximate entropy of vowel phonation spectra has been used to reveal two normal voicing groups in healthy males. An analysis of the corresponding open and closed quotients for the groups shows the first with balanced quotients and the second with asymmetric quotients characterised by pronounced vocal fold open phases. This indicates the second group is impacted by turbulent air flow, which reduces both the spectral structure in and approximate entropy of vowel phonation. The corresponding spectra are presented to confirm the effect. This provides a physiological explanation for the success of approximate entropy as a single figure of merit for voicing quality.