Sleep And Its Environment

Besides the interior factor of your particular sleep-awake cycle, various aspects of the exterior environment can have an effect on your ability to fall asleep and stay asleep. 

Noise and Sleep 

Most people underestimate the effect of noise, or lack of it, on their sleep. We all know how annoying it is to hear the dripping of a tap in another room, or the clock ticking away in the silence of the night, but some of us cannot sleep without some sort of background noise - for example, the radio playing softly or the low hum of a fan or air conditioner.

The amount of noise that we can tolerate during sleep varies tremendously from one person to another. Some people are awakened by a light 15-decibel whimper, while others can sleep soundly through noises as loud as 100 decibels, a noise level comparable to that in an all-night disco bar. Generally, much less noise is needed to awaken you in twilight-zone sleep than in deep sleep, and you are more likely to be roused by noise in the first part or in the last part of sleep, since you are more aware of changes in your environment during those stages of the sleep cycle. Interestingly, less sound is needed to awaken someone if the sound is a recognizable, meaningful one, rather than a non-specific, generic sound. Women are awakened more easily than men by a sudden noise, and young people sleep through more noise than do seniors, who are more easily awakened by minor disturbances. A noise loud enough to waken a seventy-year-old will cause only a shift into twilight-zone sleep for most twenty-five-year-old sleepers. 

It makes good evolutionary sense that sudden, unexpected noise alarms or awakens us. Remember, we are very vulnerable in sleep, so we need to be able to awaken in response to any noise that might signify danger. On the one hand, a sudden noise is more likely to be a threat to us, a source of harm, than a gentle, comforting sound. 

On the other hand, soft, steady rhythmic noise is often helpful in falling asleep. Bach's Goldberg Variations are tender and quiet piano solos written at the request of a prince who wanted some music to help him sleep. However, some people would find that listening to piano music would forbid sleep. The point is, there is quite a bit of individual variation, and you should experiment to see what works for you. Earplugs can be a help for those who seem to be aware of every little noise, and some low background sound, such as a fan running on low speed, may help muffle the faint irregular sounds the house makes as you try to rest. This effect is called "blocking" and it works for many people. Sometimes, such as when a dripping tap captures your full attention, your hearing actually becomes more acute while you are trying to go to sleep and you pick up sounds that you would normally not hear. This seeming paradox can be explained in part by the fact that the sounds you make during normal activity cease when you are trying to drop off to sleep, and the relative silence amplifies what little sound there is. Some soft, soothing, regular background noise in this situation is very helpful.