Bhishmadeva hearing such words of high esteem, roared like a lion and to gladden the heart of Duryodhana blew a thunderous blast from his conch shell.

Madhvacarya has no commentary so we present Baladeva Vidyabhusana's.

Bhishma become elated hearing the praises given him by Duryodhana. Thus to eliminate the fear he knew Duryodhana was concealing in his heart he roared like a lion, simha-nadam means roaring like a lion and then blew a thunderous blast on his conchshell. By only sounding a blast on his conch shell without speaking Bhishma signified that true to ksatriya or warrior code of warfare he would fight until death.

So Duryodhana full of internal anxiety deceptively addressed the preceptor Dronacarya attempting to conceal his fear at the might of the Pandava army. Drona understanding the offensive innuendo by the words inner significance ignored Duryodhana being dissatisfied by the subtle sarcasm concealed within the words. At this time the valiant grandsire Bhishma perceiving Duryodhana's inner despondency, roared like a lion and blew a thunderous blast on his conch shell just to increase Duryodhana's joy.