We perceive the environment differently when we sleep. But it is still unclear exactly how much the brain responds to noise during sleep. Researchers from the University of Liège (Belgium) published a study this week that used brain imaging to document its response to sounds when we sleep.
The results showed that in the face of noise, brain activity is controlled by particular brain waves while we sleep. Specifically, waves that are known as sleep spindles prevent noise from being transmitted to the auditory regions of the brain. On the other hand, there are certain sounds that are associated with K-complex brain waves. The auditory areas triggered by these types of sound would be larger.
So during sleep, our perception is not continuously reduced. Rather, it varies depending on the influence of particular brain waves.