Bhagavad Gita Chapter 1 Sloka 13 (1.13)

ತತಃ ಶಂಖಾಶ್ಚ ಭೇರ್ಯಶ್ಚ ಪಣವಾನಕಗೋಮುಖಾಃ ।
ಸಹಸೈವಾಭ್ಯಹನ್ಯಂತ ಸ ಶಬ್ದಸ್ತುಮುಲೋsಭವತ್ ॥೧೩॥
tataḥ śaṃkhāśca bheryaśca paṇavānakagomukhāḥ ।
sahasaivābhyahanyaṃta sa śabdastumulosbhavat ||13||
Sloka 1:13
Gist of the sloka:
After which, the Kaurava army raised various sounds from Conch, Drums, bugles, horns, trumpets and various other war musical instruments.
Explanation:
Following Bheeshmacharya, the various parts of Kaurava army indicated their readiness by making sounds from the various war musical instruments. These sounds were intense and ear piercing.
It is to be noted that Duryodhana nor any of his 99 brothers used their conch to indicate their readiness.
Duryodhana as their leader never assembled or led his army to any kind of readiness. For a person who has disturbed mind state, can never lead himself or his followers to any kind of victory.