But it was not the whining they could hear, it was the rush of blood which their wildly beating hearts sent pounding through their veins.
Could anyone please explain the sentence for me?
I found more context: “And all of them waited, all of them numb. And they listened, and thought they could hear the whine of the falling bomb. But it was not the whining they could hear, it was the rush of blood which their wildly beating hearts sent pounding through their veins.”
They could hear a sound. They thought this was the whining sound made by the falling bomb. However, it was not. Instead, it was the sound of blood rushing through their veins. This was especially loud because their hearts were beating so fast (presumably because they were frightened).