Bhashya
आकाश एव यस्यायतनम् ।य एवायं श्रोत्रे भवः श्रौत्रः, तत्रापि प्रतिश्रवणवेलायां विशेषतो भवतीति प्रातिश्रुत्कः, तस्य का देवतेति- दिश इति होवाच ; दिग्भ्यो ह्यसौ आध्यात्मिको निष्पद्यते ॥
In plain words
Space alone is his home. Call him 'auditory' because he arises right there in the ear; call him 'the echo-one' because he shows up exactly at the instant a sound comes back to you. Ask his god, and the answer is the directions themselves — because it's out of the four quarters that this inward self of hearing is born.
Close to the Sanskrit
'Space alone is his abode' — the one who arises in the ear is 'śrautra'; and since he arises there specially at the moment of an echo, he is 'prātiśrutka'. Of him, what is the deity? — 'The directions', he said; for it is from the directions that this inward counterpart comes to be.