ἀφώνως. The ancient custom was to pray aloud, partly from a feeling that one ought not to make any prayer which might not be heard by all mortals. Pythagoras in Clemens Alex. Strom. 4. 26 § 173 (it is usual μετὰ φωνῆς εὔχεσθαι) “ἐμοὶ δοκεῖ, οὐχ ὅτι τὸ θεῖον ᾤοντο μὴ δύνασθαι τῶν ἡσυχῇ φθεγγομένων ἐπαΐειν, ἀλλ᾽ ὅτι δικαίας ἐβούλοντο εἶναι τὰς εὐχάς, ἃς οὐκ ἄν τις αἰδεσθείη ποιεῖσθαι πολλῶν συνειδότων”.
Lucan 5. 104 “tacito mala vota susurro Concipiunt.”