1)
Why does it say that only Yo'av heard the Shofar?
1.
Malbim: The others heeded only the noise of the city. Yo'av, the head general, heard and understood the sound of the Shofar; he understood that it is a great matter.
2)
What was the question?
1.
Radak (41-42): What is the reason for this awesome noise? They know that it is connected to their act (declaring Adoniyahu king); they did not know that if it was to support them or to oppose them. Malbim - surely it is for a great matter!
