स यथा दुन्दुभेर्हन्यमानस्य न बाह्याञ्छब्दाञ्छक्नुयाद्ग्रहणाय ।दुन्दुभेस्तु ग्रहणेन दुन्दुभ्याघातस्य वा शब्दो गृहीतः ॥४,५.८ ॥
In plain words
As when a drum is beaten one cannot lay hold of the outward sounds, but by laying hold of the drum, or of the beater of the drum, the sound is laid hold of;