They're just not resonant. In place of a gut string bow, the lobster has a nub of tissue called the plectrum. This soft tissue rubs over the soft surface of a fleshy file just below the lobster's eye. The sticking and slipping motion over microscopic ridges on the file provides the lobster with its caustic sound. The sound not only resembles the violin's mechanisms, it's also created in the same way that rubbing a wet thumb over a balloon makes a squeak or the moving parts of a squeaky door hinge creak.
Spiny lobsters hear only at close range using sensory hairs.
Instead Patek thinks the noise is intended to discourage a predator such as a grouper or a shark from eating the animal. That might give you pause. The spiny lobster's noisemaking device is the only one of its kind to be detected in any animal, says Ron Hoy, a professor of Neurobiology and Behavior at Cornell University. Many other animals, such as crickets, produce noise by scraping a hard pick over a rough-edged file. The effect generates pulses of sound, much like a stick scraping over a washboard.