Vaiśeṣika Sūtra 2.2.28

2.2.28

acākṣuṣatvān na karma |

na—not; api—also Karma, action; acākṣnuṣatvāt—not being visible.

24. Nor (is Sound) an Action, because it is not an object of visual perception.

Because the intuition of perception of Sound is not visual, i.e., is produced by an external sense-organ other than the eye. So that the import is that, like the quality of Taste, etc., Sound-ness also does not reside in Actions, because it is a ‘class’ which does not reside in the objects of visual perception.—24.