During our steep cliffside descent from Montespluga, Italy, a block of wood was slipped underneath the shoe to increase friction even further.

FORBES: Antique Roadshow

That means that an object under the stack - in the team's experiments, a block of wood about 10cm long - would not "hear" the sound, and any attempts to locate the object using sound waves would not find it.

BBC: Acoustic 'cloaking device' shields objects from sound

There is a famous story about a cell phone manufacturer focusing their design solely around a small block of wood.

FORBES: What your business can learn from Lady Gaga...no, seriously.

In his basement workshop on a recent evening, Mr. Baum rotated from his drill station to his sanding station, working on a fresh block of wood.

WSJ: Gentlemen, Start Your Little Cars: These Derbies Are for Grown-Ups