Example sentence:
From behind, I heard the _ and _ of a door.
What are those two words?
Consider the pull and thud of a door.
While pull isn't ordinarily considered onomatopoeia, its pronunciation is suggestive of the sound of air rushing through as a tightly-sealed door is opened.
It depends on how the door was opened/closed. Potential words include
Perhaps the sound of the door can be left up to the imagination of the reader? The writer has already deduced that the sounds are from a door, so the whole statement could be simply:
From behind, I heard the opening and closing of a door.
Or
From behind, I heard the unlocking and opening of a door.
Or
From behind, I heard the closing and locking of a door.
Otherwise, any sound associated with a door fits. For example:
From behind, I heard the creaking and slamming of a door.
KL-
assonance in English, which have to do with things being or moving together, frequently with considerable force applied, and often making a distinctive noise. See the Venn diagram for details.