We hear the silence worse

Our attention is arranged so that in a noisy environment, we quickly notice new sounds, but they are missing that suddenly disappeared.
If around us suddenly become totally silent, of course we immediately noticed. But if in a noisy environment will disappear a few sounds, and the rest will continue to sound as extinct pass by our attention. For example, the adults talking in the kitchen while listening to the radio, do not notice the sudden silence in the baby's room. Scientists from University College London (UK) describe this feature of our attention in the article on PLoS ONE.
Scientists are trying to understand what makes some sounds more noticeable than others. To do this, they created a "soundscape", and study participants were celebrating when the next sound on and off. As it turned out, the human ear can hear very well the emergence of new sounds, but a lot less responsive to their disappearance. More diverse than was the noise, the greater the change in the sound picture of the subjects were left unattended, and the changes that have yet to notice reached the person for a longer period.
The authors emphasize that this effect was independent of the volume of noise and had a place even in the relatively simple "soundscape." That is the deciding factor was that there was a new sound, or disappear.
Obviously, this is due to the fact that our attention is focused on the current sound. In another series of experiments, the researchers distracting listening to a short tone, and then the man is worse observed changes in the ambient noise. This can partly be explained from the evolutionary point of view is more important than hear them, that is, fix it the appearance of new sounds that you can give yourself. On the other hand, it is easy to imagine a situation where silence is said of the impending danger. This is not necessarily a Hollywood thriller - think about the driver or pilot, who simply have to hear everything, and even more so the disappearance of familiar sounds in the engine.
Perhaps in the future the data will help set up a rumor of those engaged in such occupations that they have heard all of the important changes in the surrounding noise.