How is shimmer defined in the context of amplitude variation?

Shimmer is defined as the cycle-to-cycle amplitude perturbation within acoustic signal analysis. This measure focuses on the small variations that occur from one cycle of vocal fold vibration to the next during phonation. It provides insights into the stability and consistency of sound production; the more stable the amplitude, the lower the shimmer value. High shimmer values indicate greater variability in the amplitude of the acoustic signal, which can be indicative of voice disorders or instability in vocal fold vibration.

Other options, such as long-term average amplitude, average intensity over time, and peak amplitude measurement, refer to different aspects of voice and sound characteristics. Long-term average amplitude looks at the overall amplitude of the signal over a longer duration rather than specific cycle-to-cycle changes, while average intensity relates to the loudness of the voice over time. Peak amplitude measurement focuses on the maximum amplitude reached during a signal, rather than the variations in amplitude across cycles. This means that while each of these terms is relevant in the study of voice and acoustics, they do not capture the specific cycle-to-cycle variations that shimmer addresses.