وَإِنْ كَانَ مُنْفَرِدًا فَهُوَ مُخَيَّرٌ، إِنْ شَاءَ جَهَرَ وَأَسْمَعَ نَفْسَهُ، وَإِنْ شَاءَ خَافَتَ.
Meaning: If praying alone, he has a choice: he may recite audibly so that he hears himself, or he may recite quietly.
The discussion concerns the individual’s recitation in prayers whose congregational recitation is audible.