2 adjectives to describe borings

For hours on end he lay flat on his back, staring at the dim illuminations of the windows and listening to the faint out-of-door noises or the sharper borings of insects in the logs of the structure.

" So, in spite of the protests of Captain Martin, the change was made, and late that night Ned awoke to find himself sitting up on the edge of his bed, automatic in hand, listening to the steady boring of a tool of some sort around the lock of his door!

2 adjectives to describe  borings