When we sleep we are vulnerable. Eyes closed and unconscious, we appear to be unaware of our surroundings – which, from an evolutionary point of view, would put us at a distinct disadvantage.
In fact, during our sleep we wake up literally hundreds of times to check that we are still safe and secure and can thus carry on sleeping. These awakenings are very short (between 1 and 2 seconds) and we are unaware that they are taking place. If, however, we detect something in our environment that is not right – an unexpected noise, for instance – our ‘primitive’ brain needs to make sure it is not a threat and we become fully awake to process and rationalise what is going on.
However we do not wake up to each and every noise. The sound has to be ‘meaningful’ – i.e. the brain perceives it as important or a threat – for it to disturb our sleep. This means that we can actually get used to sounds that initially seem disturbing, but this will take at least a couple of weeks while our brain works out that the noise is safe to ignore.
So ideally, your bedroom should be as quiet as possible. Unfortunately, quiet often isn’t an option. In this case, you can use other sounds to distract the brain from the more disruptive noises: relaxing music or the drone of an electric fan, for instance. It doesn’t really matter what noise you use, provided that your brain does not have to actively listen to it!
Dr. Neil Stanley
Dr Neil Stanley is an independent sleep expert who has been involved in research for over 35 years. After starting out at the R.A.F. Institute of Aviation Medicine, he moved on to the University of Surrey's Human Psychopharmacology Research Unit, where he was Director of Sleep Research. Today, he travels the world lecturing on various aspects of sleep to both healthcare professionals and the public at large.