The sound of a female carpenter bee (Xylocopa virginica, the “Virginia wood-cutter”) chewing wood fibers at the end of her tunnel inside a piece of exposed wood in a barn. She’s chewing away with her sharp mandibles, making a tubular nest for her eggs. She’ll provision these with nectar and pollen, giving the young a well-protected place to start life. The mother bees overwinter in their tunnels and their offspring often bore new holes close to the natal hole. So a cluster of bees on a single board or in one part of a barn is often a family group. Here’s a photo from 2012 of a modest-sized tunnel. These borings can get much bigger, hollowing entire pieces of wood.
Surely the invention of the saw opened huge new opportunities for this species of wood chewer. Before humans came along, the bees had to wait for branches to crack open or for wood to expose itself in other ways. Carpenter bees must regard humans as evidence of intelligent design: we’re a species whose only purpose is to erect grand temples of dimensional lumber for carpenter bees. Amen, sisters. Teleology is a fine thing.