A command in the Pulses menu of the SoundEditor or TextGridEditor windows. Before changing the advanced pulses settings, make sure you understand the Voice tutorial.

For information about the Maximum period factor setting, see PointProcess: Get jitter (local).... The standard setting is best in most cases. The Period floor and Period ceiling settings derive from the pitch floor and pitch ceiling (Pitch settings...), according to a formula given in Voice 2. Jitter.