PHONETICS: Vibrato involves a frequency modulation superimposed upon the pitch frequency of the note sung. It also requires a small intensity modulation of a few decibels. On average, the vibrato range is 5-8 Hz and the intensity increase is 9 dB. Vibrato adds emotion to the singing voice when properly controlled. An excessively high number of pulsations gives rise to the unpleasant quality known as tremolo. Slow pulsations give an impression that the voice is wobbling.
Audiodemonstration the singing voice