Possible Clues:

• Dull heavy impact
• Clunk's kin
• Nickname for the Vietnam War's F-105 fighter plane
• Sound in a game of horseshoes
• Sound of heavy impact
• Graceless landing sound
• Sound of an ungentle landing
• Sound made by impact of heavy objects
• Tax cut reversed after husband invested - it sounds like a blow
• Sound right after a knockout punch