Vaiśeṣika Sūtra 2.2.36

2.2.36

saṃyogād vibhāgāc chabdāc ca śabdaniṣpatteḥ |

aṃyogāt—from Conjunction; vibhāgāt—from Disjunction; ca—and; śabdāt—from Sound; ca—and; śabda-niṣpattiḥ—production of Sound.

31. Sound is produced from Conjunction, from Disjunction, and from Sound also.

‘From Conjunction’.—i.e., from Conjunction of the drum and the drum-stick. ‘From Disjunction’—i.e., when a bamboo is being split up. Here Conjunction is by no means the cause of the first Sound, because there is then no Conjunction. Therefore the Disjunction of the two halves of the bamboo is the efficient or conditional cause, and the Disjunction of the halves and Ether is the non-combinative cause. And where Sound is produced in a distant flute, and the like, there Sound which is produced in the order of a current, leaches the portion of Ether limited by the hollow of the ear, and thereby becomes heard, therefore Sound is produced from Sound also.—31.