That sound, caused by electromagnetic interference (EMI), occurs even when a mobile isn't receiving a text message or ringing, and it can often happen when the mobile is doing what is known as a "hand shake" with a mobile tower, he said.

The "burst of electrical activity" in that hand shake affects skin nerves, causing transcutaneous muscle stimulation and giving the impression of a vibration, he believes.

He does not believe it causes any great harm to our bodies and stresses that he has not studied the phenomenon.

"If you are really perturbed by [the sensation], simply hold [your mobile] away from your skin," Professor Blaszczynski suggested. Putting your mobile in a coat pocket or leather case would mean "significantly less" vibrations felt, he added.

A colleague of Professor Blaszczynski at the University of Sydney, Professor Gerard Goggin, chairman of the Department of Media and Communications, believes that phantom vibrations occur when one is expecting "alerts and notifications" or a call or text.

"Mobiles are very much a part of our lives, " he said. "In that sense they become an extension of your body."

Checking them therefore becomes almost like a reflex, regardless of whether they were ringing or vibrating, he said.

What the studies say

Of the two studies Fairfax Media could find related to the topic, the more recent, published on December 15, 2010, concluded that the sensation, or what it called "phantom vibration syndrome", was "common among those who use electronic devices".

The study found that the prevalence of phantom vibrations in a population of medical staff using pagers and mobiles was nearly 70 per cent. The sample size was 176.

Of the 169 participants who answered a question, 115 reported having experienced phantom vibrations, it said.

The study suggested its cause might result from "a misinterpretation of incoming sensory signals by the cerebral cortex" - the thick sheet of cells on the outside of the brain.