Jitter in violin and singing-voice tones
Rudolf A. Rasch · The Journal of the Acoustical Society of America · 1985
Musical tones like those of the stringed instruments and the singing voice are not sequences of exactly repeated waveforms with constant frequency, amplitude, and spectrum. Frequency variations can be classified as jitter (random or pseudorandom period-to-period fluctuations), vibrato (quasiperiodic fluctuations with a frequency of 4–7 Hz), and trend (slow, long-term fluctuations). We have investigated a number of musical tones for the presence of jitter and will present the results of various types of measurements, like period-to-period differences, standard deviations of periods, autocorrelations of periods, etc. One of the main findings was the relation between jitter and the resonance of the sound radiating system (top plate, vocal tract). Tones with frequencies near to a resonance had considerably less jitter than tones with frequencies further removed from a resonance.