Following are a number of back-translations as well as a sample translation for translators of Isaiah 30:31:

• Kupsabiny: “The people of Assyria shall faint when they hear the noise/shouting of God.
  God shall crush those people.” (Source: Kupsabiny Back Translation)
• Newari: “Having heard the voice of the LORD, Assyria is trembling.
  He will strike them with his scepter.” (Source: Newari Back Translation)
• Hiligaynon: “Surely those of/from-Asiria will-be-terrified when they hear the voice of the LORD. He will-punish them very severely(double intensifier).” (Source: Hiligaynon Back Translation)
• English: “The soldiers of Assyria will be terrified when they hear the voice of Yahweh
  and when he strikes them with his rod.” (Source: Translation for Translators)