。
The wall collapsed with a loud crash.
Literal
Wall [topic-は] big sound [object-を] making rumblingly fell.
ガラガラ is a 擬音語 (sound mimetic) for rattling, rumbling, or crashing sounds — here describing the noise of a wall collapsing. 音をたてて means 'making a sound.' The combination 大きな音をたててガラガラと倒れた is vivid and cinematic.