What is vocal shimmer?
Shimmer measures cycle-to-cycle variation in the amplitude of a voice — the loudness counterpart to jitter, and what an elevated reading means.
The measurement
Shimmer is how much the amplitude of each vocal fold cycle differs from the one before it. Where jitter asks whether the cycles are evenly spaced in time, shimmer asks whether they are evenly sized.
It is reported either in decibels or as a percentage. A voice with high shimmer sounds rough or breathy even when the pitch is steady, because the tone is fluctuating in loudness faster than a listener can follow consciously.
What counts as high
Around 3% (roughly 0.35 dB) is the figure usually cited as the upper edge of normal for a sustained vowel, though the number depends heavily on the vowel, the pitch, and the analysis method — which is why any single threshold should be read as a rough boundary rather than a line.
In a sentivoice report shimmer contributes to the vocal strain score alongside jitter and harmonics-to-noise ratio rather than being scored on its own. No single perturbation measure is reliable enough by itself to be worth acting on.
What moves it
Incomplete vocal fold closure is the main driver, which is why breathy singing raises shimmer even when it is a deliberate stylistic choice. Fatigue and irritation raise it too. Microphone distance does not — shimmer is a cycle-to-cycle ratio, so a quiet recording and a loud one of the same performance produce the same number.
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Run a 30-second quick checkCommon questions
Can shimmer be too low?
Not in any way that matters for a singer. Very low perturbation is what a synthesised tone has; a healthy human voice sits comfortably above zero and is not trying to reach it.
Does singing breathily on purpose count as strain?
It raises the measurement, because the measurement describes the signal rather than the intent. A deliberately breathy pop vocal will read as higher shimmer than the same singer belting cleanly. Read the number alongside what you were trying to do.