Which perturbation measure is used to determine the amount of noise in the voice?

• A. Changes in the frequency range between F1 and F2 over time
• B. Changes in the frequency range between F2 and F3 over time
• C. F3 cycle-to-cycle variations in sound energy over time
• D. F0 cycle-to-cycle variations in sound energy over time

Answer: (D)

In voice analysis, the amount of noise is best captured by how stable the pitch is from one vocal cycle to the next. This is measured by looking at cycle-to-cycle variations in the fundamental frequency, F0. When the vocal folds vibrate very regularly, F0 remains nearly constant from cycle to cycle, giving a low jitter value. If there’s more noise or instability, those cycle-to-cycle fluctuations in F0 increase, and jitter rises, reflecting a rougher, noisier voice.

The other ideas focus on different aspects: shifts in formant frequency ranges (which reflect vocal tract resonances and articulation rather than vibration stability) and variations in energy tied to higher formants (which would relate to amplitude changes, not pitch stability). So the measure that directly quantifies the noisy, unstable vibration is the cycle-to-cycle variation in F0.