Voice 2. Jitter

You can measure jitter in the Sound editor window, after choosing Show pulses from the Pulses menu. You will see blue lines that can be thought of as representing the glottal closures. Use Voice report from the Pulses menu to get the jitter in the selected part. You typically perform jitter measurements only on long sustained vowels.

The voice report gives five kinds of jitter measurements. All of these measurements are based on the computation of all periods by the waveform-matching procedure (see Voice 6. Automating voice analysis with a script), where the Period floor setting is 0.8 divided by the pitch ceiling, the Period ceiling setting is 1.25 divided by the pitch floor, and the Maximum period factor is determined in Advanced pulses settings....

Jitter (local)

This is the average absolute difference between consecutive periods, divided by the average period. For the precise procedure, see PointProcess: Get jitter (local)....

MDVP calls this parameter Jitt, and gives 1.040% as a threshold for pathology. As this number was based on jitter measurements influenced by noise (see Voice 5. Comparison with other programs), the correct threshold is probably lower.

Jitter (local, absolute)

This is the average absolute difference between consecutive periods, in seconds. For the precise procedure, see PointProcess: Get jitter (local, absolute)....

MDVP calls this parameter Jita, and gives 83.200 μs as a threshold for pathology. As this number was based on jitter measurements influenced by noise (see Voice 5. Comparison with other programs), the correct threshold is probably lower.

Jitter (rap)

This is the Relative Average Perturbation, the average absolute difference between a period and the average of it and its two neighbours, divided by the average period. For the precise procedure, see PointProcess: Get jitter (rap)....

MDVP gives 0.680% as a threshold for pathology. As this number was based on jitter measurements influenced by noise (see Voice 5. Comparison with other programs), the correct threshold is probably lower.

Jitter (ppq5)

This is the five-point Period Perturbation Quotient, the average absolute difference between a period and the average of it and its four closest neighbours, divided by the average period. For the precise procedure, see PointProcess: Get jitter (ppq5)....

MDVP calls this parameter PPQ, and gives 0.840% as a threshold for pathology; as this number was based on jitter measurements influenced by noise (see Voice 5. Comparison with other programs), the correct threshold is probably lower.

Jitter (ddp)

This is the average absolute difference between consecutive differences between consecutive periods, divided by the average period. For the precise procedure, see PointProcess: Get jitter (ddp)....

This is Praat's original Get jitter. The value is three times RAP.

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© ppgb, March 2, 2011