A team at Harvard Medical School claims that a section of the brain, known as thalamus, plays a key role in blocking out sound during sleep and it appears to be more effective in certain individuals.

Normally brainwaves slow down during rest, but brain still generates brief energy bursts called sleep spindles.

Lead scientist Jeffrey Ellenbogen said: "The thalamus is likely preventing information from getting to areas of the brain that react to sound. A sleep spindle is a marker of this blockade. The more spindles your brain makes, the more likely you'll stay asleep, even if confronted by noise."

For the study, the scientists analysed 12 healthy volunteers at a sleep clinic over the course of three nights. They were monitored each night using an electroencephalograph which records the electrical activity of the brain.

The first night was quiet but during the second and third nights, volunteers were confronted with the sounds of telephones ringing, road and air traffic noises and the beep of hospital equipment.

The team detected patterns known as sleep spindles which are thought to block out the effects of sound and other sensory information passing through the brain.

Individuals with the highest rates of spindles on the quiet night were less likely to be woken by noises on the second and third nights, and some were not even aware their sleep had been disrupted, Ellenbogen said.

The scientists hope to eventually use this finding to enhance the natural brain rhythm that protects sleep.

"Our study demonstrates this finding in humans, and takes it one step further - one can use the sleep spindle as a biomarker for predicting whether a person will have difficulty in noisy environments or not in the future.

"We have a lot of work to do before using this in people, mostly because we want to be absolutely clear that this is safe and effective. But whether it's next year or next decade, this research will lay the groundwork for brain-based solutions to noisy environments," Ellenbogen said.