Should supererogatory prayers be recited audibly or silently?

The ruling regarding vocalization and

silencing in supererogatory prayers varies according to the type of prayer. Vocalization is

Sunnah for Eid prayer, الاستسقاء (prayer for rain), Tarawih, and lunar eclipse

prayer, without any difference of opinion. As for daytime supererogatory prayers,

silencing is Sunnah without any difference of opinion. Regarding nighttime

supererogatory prayers, other than Tarawih, some jurists say that vocalization is

Sunnah, while others say that an intermediate level between vocalization and silencing is

Sunnah. As for the regular Sunnah prayers accompanying the obligatory prayers, they are

all to be performed silently, by the consensus of the jurists. It was reported from some of

the Salaf that vocalization is permissible in the Sunnah prayer of Fajr, but the majority of

scholars hold the opinion of silencing. It is recommended to vocalize in nighttime

supererogatory prayers and to silence in daytime supererogatory prayers, although

vocalizing in the daytime is permissible.