In fact, vocal tremor in healthy individuals (physiological tremor) has been measured, showing modulation rates below 5 Hz. The presence of such modulations by itself is not an indicator of dysphonia instead, the presence of tremor is necessary for a natural sounding voice. Acoustic analysis of the voice aimed at detecting, measuring, or modeling instabilities due to vocal tremor is usually approached by seeking for modulations in the sequence of pitch periods (e.g. This is coherent with the nature of voice tremor, that is, instabilities in the voice production system are better noticed when a stable phonation task is performed. The presence of vocal tremor in the acoustic signal is better perceived in the phonation of sustained sounds than in running speech. While vocal tremor happens during speaking, vibrato is a feature of the singing voice that may express emotions such as anger, happiness, fear, or sadness. Similarly, vibrato is a modulation of the acoustic voice signal too, but vocal tremor differs from it in that for vibrato, the span of typical modulation rates is narrower (between 4 and 7 Hz) and the modulation is more cyclic.
It differs from voice amplitude and frequency perturbations in that while these are random and fast deviations from stable underlying values of amplitude and fundamental frequency, vocal tremor involves an instability in such values. Vocal tremor happens at a rate well below the fundamental frequency, between 1 and 15 Hz. modulation) in the amplitude or frequency (or both) of voice. Correspondingly, vocal tremor can be defined as a low-frequency fluctuation (i.e.
Tremor can be defined as an involuntary oscillatory movement of a body part.