Is there an authoritative source stating that in order to be a liturgical act, the Liturgy of the Hours must be prayed vocally as opposed to silently? This question comes up on the regular forums now and then, but the answers seem to be just opinions. I would like to see something in a modern (post Vatican II) document if possible.
I understand the logic of it: the Liturgy of the Hours is the public prayer of the Church, rather than something going on inside your own head, even if you are by yourself. I believe a priest saying mass by himself is similarly obliged to say everything out loud, at least in a whisper. I would just like some kind of explicit documentation of this. The General Instruction of the Liturgy of the Hours does not spell out this requirement, although several priests have told me that they were taught this in the seminary. I’d just like some sort of reference for the sake of some research I’m doing.