noun / verb
thud
THUD/θʌd/
A dull, heavy impact sound, or to make such a sound.
The heavy sack hits the floor with a thud.

Etymology
The word is broadly imitative of sound and may have been coined more than once. Its modern use evokes the low, blunt noise of a heavy impact.
In context
use a spoon and tap gently on the lid a clear ringing sound indicates a sealed jar while a dull thud tells us it hasn't sealed