Effect of continuous traffic noise on percentage of deep sleep, waking, and sleep latency.

When subjected to alternating quiet nights (32 dB) and noise nights (equivalent levels of 47 dB) a group of 14 subjects showed an average increase in the fraction of deep sleep of about 2. 5% resulting from traffic noise. Another group of 12 subjects whose nights were at 60 dB had an average of 4. 6% in deep sleep during these nights. The number of waking also increased for both groups but, as found before, this adapted rapidly with the number of nights.