What is "whuffling"

Usage examples of "whuffling".

Rothan was glaring into space with bloodshot eyes, making little whuffling noises deep in his throat.

He lay on the ledge and giggled, softly, a whuffling intake and outgo of air, then he did his breathing exercises, slow the breath, in-out, in-in-in until his body ached, out-out-out until he was empty, again and again, until he was wholly relaxed, limp, almost asleep, breathing the cool odorous smell of the stone, the sealants that made the room potentially airtight, fugitive traces of robot stink and other traces it was not possible to identify.