monotone sounds with high frequency (high pitch), specifically with wavelengths shorter than the width of your head, are difficult to localize by your brain/hearing system. this is because your brain uses both differing volume and phase from each ear to determine where a sound is coming from. if you have been plagued by a rogue cricket in your house you will know what i mean..that thing can literally be in behind you croaking at full volume and you would not be able to tell where it is coming from. white noise has multiple frequencies which will be easier to localize.<br><br>where safety is concerned the researchers have concluded that it is not necessarily crucial that you immediately know what the hell is making that white noise, but instead it is far more important that you will notice it at all and will be able to more effectively identify the direction the source when you do.