स यथा शङ्खस्य ध्मायमानस्य न बाह्याञ्छब्दाञ्छक्नुयाद्ग्रहणाय शङ्खस्य तु ग्रहणेन शङ्खध्मस्य वा शब्दो गृहीतः ॥२,४.८ ॥
In plain words
and as when a conch is blown one cannot lay hold of the outward sounds, but by laying hold of the conch, or of the blower of the conch, the sound is laid hold of;
The commentators
Bṛhadāraṇyakopaniṣadbhāṣyam· bhāṣya
तथा स यथा शङ्खस्य ध्मायमानस्य शब्देन संयोज्य- मानस्य आपूर्यमाणस्य न बाह्यान् शब्दान् शक्नुयात्- इत्येवमादि पूर्ववत् ॥
In plain words
The same holds for the next line too: 'as when a conch is blown, joined with sound, filled with sound, no one can seize its scattered outer sounds' — and so on. Take it exactly as explained before.
Close to the Sanskrit
Likewise, [the clause] 'as, of a conch being blown, being united with sound, being filled up, one would not be able [to grasp] the external sounds' and so on, is to be understood as before.