GUANGZHOU, CHINA — Alleged cases of "sonic attacks" in China and Cuba has raised the question of how sound can used as a weapon.

U.S. diplomats in Guangzhou, and previously Havana, have been diagnosed with unexplained brain injuries following abnormal sensations of sound and pressure, prompting fears of a sonic weapon, The New York Times reports.

Ultrasound is a possibility, but an unusual weapon choice: it loses power with distance more quickly than audible sounds, and requires precise alignment with a subject.

University of Maryland researchers theorized that the illness may have resulted from surveillance gear being positioned too closely together.

Ultrasonic devices can interfere with each other in a phenomenon known as intermodulation distortion, producing audible sound similar to what patients claimed to hear.

When placed at too close range or combined with other ultrasonic emitters, these devices can cause cavitation damage, causing bubbles to form in body fluids, tissues, or cells.

It's hard to say for certain what exactly triggered the diplomats' mystery ailments, but more than one expert has chimed in to say bad engineering or a bad spy job is more plausible an explanation than a sonic attack.