What is "tunks"

Usage examples of "tunks".

She collapsed the tingler fence and tucked it in her pack, smoothed her hand down the outside of the harp case, tapped her fingers on the leather, snapped it open, touched the loosened strings, sighed at the dull toneless tunks she produced.

Rain dripping in sharp brittle tip tap tunks about her, Ti-cat slid through the deep shadow under the huts, nervous because those high floors suggested strongly that predators like the skitterdiscs prowled here at night.