The rattling, sucking sound of the Dementors were fading.
摄魂怪格格作响的吮吸声渐渐远去。
英语百科
Giant sucking sound
（重定向自Sucking sound）
The "giant sucking sound" was United States Presidential candidate Ross Perot's colorful phrase for what he believed would be the negative effects of the North American Free Trade Agreement (NAFTA), which he opposed.