Can What You Can’t Hear Hurt You?
By Margaret Hutchison Ph.D

Researchers have found that largely inaudible ultrasound signals from many electronics may be behind headaches and dizziness in some people. These ultrasound beams are emitted by sensors and other devices, including smart street lights, smartphone apps fire alarms and self-driving cars, to name a few.

Headaches and dizziness are among the symptoms reported by some U.S. diplomatic personnel stationed in China and Cuba in the past year after becoming incapacitated.

Ultrasonic signals are almost everywhere but the side-effects from many of transmissions remain a mystery. Ultrasonic is the workhorse of electronics, an essential part of devices such as public address systems, automatic door openers, security systems, motion detectors and automatic lights, to name a few. Typically, all but a few people can hear these signals.

However, Siri, Alexa, Google Now, Cortana and other speech-recognition systems do hear these signals. At concerts organizers broadcast an inaudible signal while musicians play to “watermark” the performance.

The growth of ultrasonic devices and applications has outstripped any sort of guidelines for their use. Most guidelines haven’t been updated since 1984, which was before most of today’s devices were invented.
Timothy Leighton, at the U.K.’s University of Southampton, has founded a research group called Health Effects of Ultrasound in Air. In his studies of exposure in public places, he found that ultrasonic noise occasionally caused headaches, dizziness, and nausea among unsuspecting pedestrians, but the effects were always temporary.

In early June, the State Department sent a medical team to Guangzhou to screen U.S. personnel and their families to evaluate them for reported headaches and dizziness. They issued a health alert for citizens traveling in China, warning that symptoms, including dizziness, headaches, fatigue, cognitive issues, visual problems, hearing loss and difficulty sleeping.

The State Department has declined to discuss its investigation into the alleged attacks, or the possibility that ultrasonic signals were a factor. Researchers in the U.S. and China who specialize in ultrasonic cybersecurity suggest that high-frequency noise generated by a badly engineered eavesdropping device could be at fault. There has been a suggestion that the intersection of ultrasound beams is the culprit. Such beams can be transmitted by surveillance or security devices ss well as normal room sensors—or by someone trying to take remote control of a smartphone.

As ultrasonic devices become ever more common, much more information will be needed in understanding the generation and effects of ultrasonic sounds.

By Margaret Hutchison Ph.D