"When the word [(verbo)] has been conveyed to you, does not the sound seem to say: The word ought to grow, and I should diminish? The sound of the voice [(Sonus vocis)] has made itself heard in the service of the word, and has gone away, as though it were saying: My joy is complete."
St. Augustine, Sermo 293.3 (PL 38, cols. 1328-1329), as translated in Liturgy of the hours, vol. 2, p. 261. I have not checked PL 38 directly, but only this rekeying.