Sleep, or the lack of it, has been the bugbear of long-haul crew and passengers alike. But brain- wave synchronisation could end the misery

Picture the scene: a passenger airliner under way on a long-haul flight. In need of rest, a pilot is relieved from his cockpit. He is not especially tired, but knowing he needs a break, he settles into his bunk and dons a set of headphones. Within 20 minutes, he is in a deep sleep, a state in which he will remain for hours before waking completely refreshed and revitalised.

The aircraft's passengers have done the same. Far from being exhausted and jet-lagged on reaching their destination, they are ready for a full day's activity.

Some may regard such scenarios as fantasy. As aircrew, passengers and airlines are all too aware, few people are able to sleep well in flight. And the debut of ultra-long-range aircraft means that crew rest issues are emerging as hot topics for both airlines and pilot groups such as the International Federation of Air Line Pilots Association.

In response, UK-based aircraft interiors manufacturer AIM Aviation is developing a device that promotes healthy, drug-free in-flight sleep using sound patterns complemented by next-generation mood lighting to create various brain states - including sleep. "My ambition is to induce people into the most satisfying, dreamless sleep I can, irrespective of tiredness," says AIM technical director Rolf Startin.

"The brain has the ability to synchronise with external audio or visual stimuli. It's a response referred to as the frequency-following response [FFR]. A technique for achieving this synchronisation is known as binaudio beat-frequency stimulation [BBFS]," he adds. AIM intends to apply BBFS via "a small device that standard-issue headphones will plug into". The system is "especially targeted at future interiors furnished with limited-availability bunks", compartments for aircrew or passengers, which could be booked for hours at a time. Users could use the BBFS facility to drop quickly into deep sleep, without having to go through lengthy rapid-eye movement sleep or "nodding-off time".

The use of BBFS was at the core of a US patent issued to Robert Monroe in 1975 for a technology known as Hemi-Sync. According to Monroe's Virginia, USA-based research and educational organisation, the Monroe Institute, specific combinations and sequences of sound can lead the brain into states of deep relaxation or alertness: "When the brain receives a different frequency from each ear, through the use of stereo headphones, it generally responds by 'hearing' a third frequency - the difference between the two incoming ones. If this third frequency relates to a certain state of consciousness, the brain falls into this state."

According to the theory, four different groups of electro-encephalogram (EEG) waves are produced by the brain, with a person's state of consciousness revealed by the frequency of the waves produced: alpha (0.5-4Hz), delta (4-7Hz), theta (8-12Hz), and beta (13-35Hz), which all correspond to particular phases of mental activity.

"If FFR is manipulated from 20Hz down to .05Hz in a precise fashion, lingering in the theta region, then your mind naturally synchronises and follows it down, and you are on the brink of restful sleep without any conscious effort," says Startin. The BBFS system would incorporate white noise, such as the sound of surf, to mask the FFR frequencies.

When used with the visual equivalent of BBFS, a "mesmeric" next-generation cabin/bunk lighting system (also developed by AIM) which replicates a twinkling, starry sky, the effect on an individual can be to stimulate the production of the hormone melatonin. Naturally produced by the body at night, the chemical is crucial to relaxation and sleep.

The scientific community is divided on BBFS' potential. Steve Hackley, a specialist in cognitive neuro-science at the University of Missouri, says: "If some researcher has shown that repetitive sounds can make someone drowsy, I would be quite sceptical that the reason is because the sounds trigger an FFR that is similar to the EEG of sleepiness."

Insomnia treatment

But a 1997 study conducted by researchers from Duke University Medical Centre in North Carolina, and the University of Virginia School of Nursing's Centre for the Study of Complementary and Alternative Therapies suggests the use of binaural auditory beats "can affect psycho-motor performance and mood".

A study of the potential of binaural auditory beats for improving sleep for victims of primary insomnia is under way at Norwalk Hospital Sleep Disorders Center in Connecticut, USA. It is to due to be completed in the first half of next year. Center director and lead researcher Ed O'Malley says the aim is to provide scientifically validated evidence that binaural auditory beats can help induce sleep. " We plan to gather enough data to test the idea that binaural auditory beats encourage sleep in insomniac patients," he says.

Primary insomnia sufferers complain of unrefreshing sleep or difficulty in falling or staying asleep, a condition associated with fatigue, tiredness, irritability or inability to concentrate - all of which can obviously affect daytime functioning. O'Malley describes the study as "double blind - that is, neither the subject nor the doctor will know who is receiving the experimental audiotape with the sound stimulus embedded in a pleasant background noise, and who the placebo audio tape with background noise alone."

The study will consist of a baseline sleep analysis, followed by a two-week period in which subjects will be given a pillow, stereo speakers and the audiotape, and asked to listen to it every night. They will then fill out daily sleep logs, registering mood and degrees of alertness, O'Malley says. After a fortnight, subjects return to the laboratory for another overnight test while listening to the audio tape for comparison to baseline test results.

O'Malley's study is not aimed at fliers generally. But having already treated pilots for sleeping problems, he points out that they are forbidden even such sleeping aids as the recently available Sonata, a quick-acting hypnotic agent. "If binaural-beat technology actually deepens or enhances sleep in measurable ways, this would be an extremely beneficial aid to pilots as well as to any group that needs to maintain or reach maximum alertness immediately upon awakening," O'Malley says.

How far off is the application of such a concept on actual aircraft? The British Air Line Pilots Association, for its part, says that the idea "sounds interesting". But until scientific or medical proof of the claimed benefits is available, it says, "the most important aspect for crews is the provision of a suitable environment in which to sleep, taking into account issues such as noise, lighting and the general comfort of the individual".


Virgin Atlantic, a recognised leader in the promotion of in-flight well-being, says it is further refining its existing eight-setting ambient lighting system for passenger areas. The airline's design team is also developing plans for crew-rest facilities on the Airbus A380, an aircraft at the forefront of the debate on crew rest.

"I think that it is too difficult to be over-prescriptive about defining a standardised solution" to crew-rest problems, says aircraft interiors consultant Paul Sillers. "There are too many variables - the presence or absence of sound, light and smells from the galleys or toilet compartments, and privacy, for example." He adds, however, that properly rested crews can only enhance the passenger experience, and he suggests that it is in manufacturers' interest to propose "initiatives, standards and amenities" to address the needs and concerns of senior cabin crew, who are involved in the airlines' aircraft procurement process. Startin, for his part, acknowledges that many will view AIM's project as "too touchy feely or airy fairy" for an industry under siege. But if he can realise its potential, BBFS could come to be regarded as a travel necessity.

Source: Flight International