The advance of a massive, terrifying force is accompanied by a deafening noise that shocks all who hear it. The primary approach among commentators is that this depicts a devastating plague of locusts. Even though these insects do not have voices of their own, the collective rustling of millions moving as one creates a roar that can be heard from far away [ביאור שטיינזלץ]. Alternatively, another perspective suggests this describes the Babylonian army, whose soldiers use loud shouts and cries to strike fear into the hearts of the people [אברבנאל].
As the force advances, the auditory imagery shifts. Initially, the sound resembles the heavy clatter of chariots. The invaders leap and jump across the mountain peaks [מצודת ציון]. Because they are positioned so high up, the noise they make echoes and travels over vast distances [מצודת דוד, אברבנאל]. There is a deliberate contrast here: ordinary chariots cannot climb steep, high terrain. Yet, this invading force easily leaps over the mountaintops while producing a massive noise equal to the rumbling of heavy chariots [אבן עזרא, רד״ק, מלבי״ם].
The nature of the sound then changes, resembling the crackling of a blazing fire consuming thin straw [מצודת ציון]. The rapid, destructive sweep of the force produces a loud snapping and popping noise, much like flames quickly burning through thin wood [רש״י, רד״ק, אברבנאל, ביאור שטיינזלץ]. Since the sheer destruction caused by the invasion is already similar to a fire, adding the distinct crackling sound completes the overwhelming sensory picture [מלבי״ם].
In the final stage of their deployment, the invaders appear as a mighty, highly organized military force arranged in precise formations [אבן עזרא, מצודת ציון]. They prepare to descend from the mountains into the cities, fully equipped to battle anyone who tries to stand in their way [מלבי״ם]. As they move, they let out a fierce battle cry designed to panic those facing them [רד״ק]. For those who view this as a description of the Babylonians, this imagery highlights their nature as a powerful nation that knows no peace, having been trained and disciplined in warfare from their youth [אברבנאל].