Sensory Short-term memory
Actually, we never hear a word all at once either, or for that matter, not even a phoneme. What we actually hear is a sustained crackling noise.
It takes a battery of short-term memory processes to achieve recognition. This first of these processes in the battery is what I would call Sensory Short memory.
The auditory modality in particular includes a process, which provides an experience analogous to the afterglow
of the blips on a radar screen. This process holds on to the blips long enough (in milliseconds) to show relationships. Similarly patterns of overtones can be discerned through Sensory Short-term memory.
Hence, we can recognize phonemes as if we heard them in their entirety. Here, in the Notes, are other descriptions of sensory memory:
NOTES: Take a short-term memory test--I dare you!
NOTES: Yet more information on Sensory-Short-term Memory.