News last month that American diplomats working at the American Embassy in Havana, Cuba, were getting sick with headaches, dizziness and hearing loss made front-page headlines. Some individuals reportedly suffered even more severe symptoms, including a blood disorder and mild traumatic brain injury.

Baffled, the State Department called on specialists at the University of Miami to investigate. Their analysis, as presented in a statement by Secretary of State Rex W. Tillerson, is that the staff had been subject to "health attacks" allegedly caused by prolonged exposure to some kind of sonic wave machine. Experts on espionage chalk it up to just another instance of long-standing, ongoing harassment by the Cuban government of U.S. diplomatic personnel.

Although in this case the symptoms appear to be have been induced deliberately, similar symptoms have been reported in a number of other cases resulting from building vibration. Much attention has been paid to the problem of noise in the built environment, particularly in regard to the workplace and healthcare facilities.

Unwanted noise of many kinds has been shown to increase stress, induce physical uneasiness, reduce productivity and raise levels of employee absence. Less attention has been paid to the issue of building vibration, but its effects can be much worse than those of ambient noise.

Building vibration can result from two major sources:

• vibrations created inside the building by machinery, electrical systems, heavy foot traffic or the movement of heavy items, such as furniture
• vibrations created outside the building from passing traffic, nearby railroad or subway lines, winds and seismic activity

Depending on the source and its proximity, it may or may not be audible to people inside the building. The effects of the vibrations can be considerable nonetheless.

In an extensive article for the Daily Mail, reporter John Naish relates the story of a woman who mysteriously began to suffer from nausea, constant anxiety and sleeplessness that resulted in substantial weight loss. After a year of consultations and tests, her doctors could not account for her symptoms.

Doing some internet research of her own, she came across something called "whole-body vibration syndrome," which is normally associated with people who operate heavy machinery but matched her symptoms accurately. She also learned that other tenants in the high-rise apartment building in which she and her son resided experienced similar symptoms, such as blurred vision, diarrhea and nausea.

Reports Naish, she "complained to the city council and contacted solicitors, who employed a specialist environmental safety company to test the building. Their equipment showed that the vibration vastly exceeded normal safety levels." She and the other tenants have since been refunded their rent and rehoused.

Naish's article, which is well worth a read, cites several research studies documenting the effects of vibration syndrome, both mild and more severe. He also mentions the creation of a "new [United Kingdom] government-funded research facility, which will open in autumn 2018, that plans to put thousands of volunteers into virtual-reality simulators that replicate the experience of working in a high-rise office block that is vibrating or swaying at low frequencies. Engineers, doctors, physiologists and psychologists will study how this affects different symptoms of motion sickness, such as tiredness, low mood, difficulty concentrating and demotivation."

An article published in June 2016 on the website for the magazine Consulting-Specifying Engineer advises builders and technicians, "For optimal occupant comfort and facility functionality, attention to noise and vibration issues should be included early and throughout the building design and construction process."

It refers builders to the noise criterion (NC) curve recommended by ASHRAE for controlling both noise and building vibration: "Vibration criteria is tied to NC, in that structure-borne noise radiated from building elements should not produce audible sound beyond the airborne NC for any given space. Vibration isolation also is intended to reduce vibration that can be felt but is below the audible spectrum."

Building owners and occupants need to be aware that those inaudible vibrations could make them feel stressed, anxious, dizzy or worse.