Charles Spurgeon Commentary Exodus 32:15-17

"And Moses turned, and went down from the mount, with the two tables of the testimony in his hand; tables that were written on both their sides; on the one side and on the other were they written. And the tables were the work of God, and the writing was the writing of God, graven upon the tables. And when Joshua heard the noise of the people as they shouted, he said unto Moses, There is a noise of war in the camp." — Exodus 32:15-17 (ASV)

And the two tables of the testimony were in his hand: the tables were written on both their sides, on the one side and on the other were they written. And the tables were the work of God, and the writing was the writing of God, graven upon the tables. And when Joshua heard the noise of the people as they shouted, he said unto Moses, There is a noise of war in the camp.

For Joshua was a younger man than Moses, and also a soldier, so his ear was quicker to hear what he took to be "a noise of war in the camp."

And the two tables of the testimony were in his hand: the tables were written on both their sides; on the one side and on the other were they written. And the tables were the work of God, and the writing was the writing of God, graven upon the tables. And when Joshua heard the noise of the people as they shouted, he said to Moses, There is a noise of war in the camp.

Joshua had probably waited lower down, and he met Moses in his descent. He heard with the quick ears of a soldier, and his thoughts went that way.