What does the Amplitude Perturbation (Shimmer) specifically measure?

Amplitude Perturbation, commonly referred to as Shimmer, specifically measures the variation in loudness over time during vocalization. It quantifies the short-term variations in the amplitude of the sound waves produced by the voice, indicating how consistent or variable the loudness is. This measurement is important in the field of speech-language pathology as it can provide insights into the stability of the vocal signal. A higher shimmer value may suggest more pronounced fluctuations in loudness, which can be indicative of various voice disorders or issues with vocal control.

Understanding the other choices sheds light on why they do not align with the concept of Shimmer. The variation in frequency over time relates to pitch modulation, which is a different parameter and is typically measured by a related but distinct concept known as jitter, not shimmer. The overall pitch range refers to the breadth of pitch that a person can achieve, which is not focused solely on the variability of amplitude. Duration of vocalization concerns how long a person can sustain a sound, rather than how loud or soft it is over time. Thus, the focus on variability of loudness firmly situates shimmer as a key measure within voice analysis.