Various Laryngeal Mechanisms in Controlling Voice Fundamental Frequency

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It is generally considered that muscular control for voice fundamental frequency (FO) is preformed mainly by the cricothyroid muscle. However, it is assumed that the whole FO range produced by humans can not be obtaind by cricothyroid activity alone. This study is intended to reveal various laryngeal mehanisms in controlling FO. Electromyographical analyses were performed on the variations in EMG activity of some laryngeal muscles associated with FO variations in word utterances. The results wereused for speculating on the mechanisms of FO control by these muscles. First, the cricopharyngeus (CP) exhibits an inverse correlation with FO, suggesting that the contraction of this muscle can rotate the cricoid cartilage forward by a combined effect of the thickening of the muscle and larynx lowering. Second, the lateral cricoarytenoid (LCA) shows the highest correlation with FO, indicating that the medial compression force can adjust effective length of vocal fold vibration in FO rasing and FO lowering. Third, the oblique part of the cricothyroid (CT) has a higher correlation with FO than the straight part, and it is speculated that the straight part produces fast FO change associated with laryngeal articulation for devoicing and that the oblique part functions to expand fo range independently with articulatory gestures. These speculated mechanisms explain the observed non-linear relation between vocal fold length and FO.