Vaiśeṣika Sūtra 2.2.30

2.2.30

sato liṅgābhāvāt |

sataḥ—of (Sound as) existent; liṅgābhāvāt—from the absence of mark.

26. (Sound does not exist before utterance), because there is no mark of (Sound as) evistent (before utterance).

For, if Sound were existent (before and after utterance), then there would be found some ‘mark,’ i.e., additional proof, of it as existent. But in the state of non-hearing, there is no proof that Sound exists. Therefore it is only an effect, and not something which reqṅires to be revealed only.—26.