John Calvin on John 12:29

29. That it thundered. It was truly monstrous, that the assembled multitude were unmoved by so evident a miracle. Some are so deaf, that they hear as a confused sound what God had distinctly pronounced. Others are less dull of caring, but yet take away much from the majesty of the Divine voice, by pretending that it was an angel who spoke. But the same thing is practiced every day; for God speaks plainly enough in the Gospel, in which is also displayed the power and energy of the Spirit, which ought to shake heaven and earth; but many are as little affected by the doctrine, as if it only proceeded from a mortal man, and others consider the word of God to be confused and barbarous, as if it were nothing else than thunder.

But a question arises: Did that voice sound from heaven without any profit or advantage? I reply, what the Evangelist here ascribes to the multitude belongs only to a part of them; for there were some besides the Apostles who did not interpret it so badly. But the Evangelist intended to point out briefly what is commonly done in the world; and that is, that the greater part of men, while they hear God, do not hear him though he speak plainly and distinctly.