Vow of Silence / Mauna
Vow of silence as an external, no-speech, vow is worthless if it does not include internal silence of the thoughts-creating / thought-replying psychic feature of the mind.
Not speaking physically may mean an increase is psychic discourse. That cannot be a vow of silence in real terms. All the same speaking externally does not mean that a person does not have some greater degree of control over the language/pictorial medium in the mind.
How much value should one give to speaking and hearing during the course of the day when one meets people at a public place, in the home or at the employment? If one gives little value to that, then during meditation one may be able to maintain silence, instead of the usual chit chat which the mind aggressively completes especially when one sits to meditate or to find some quiet time.
If during meditation, if during silence time, if after taking a vow for silence, one continues with the internal dialog, then one should admit failure.
At least if one speaks externally after taking a vow of silence one may be assisted to improve after hearing the curt remarks of critics and of people who like to ridicule.
But who will know what goes on in the mind as to if it is the most noisiest place on earth, even when the mouth is clamped shut, the eyes are closed and the ears are waxed over?