...这是个倒装句.over在这里是声音盖过,声音大过,此句意为：交通噪声太大,盖过了他说的话,（所以）我听不清他说的话.还原此句应为：the noice of the traffic over his words,so i couldn't hear what he said.
我觉得应该就是这样- -表示本妹纸也是学生党,可能有不对的地方,不对再改:)