Refining previous Community Noise Guidelines issued in 1999, and incorporating more recent research, the World Health Organization has released a comprehensive report on the health effects of night time noise, along with new (non-mandatory) guidelines for use in Europe. Rather than a maximum of 30dB inside at night (which equals 45-50dB max inside), the WHO now recommends a maxiumum year-round outside nighttime noise average of 40db to avoid sleep disturbance and its related health effects. The report notes that only below 30dB (outside annual average) are “no significant biological effects observed,” and that between 30 and 40dB, several effects are observed, with the chronically ill and children being more susceptible; however, “even in the worst cases the effects seem modest.” Elsewhere, the report states more definitively, “There is no sufficient evidence that the biological effects observed at the level below 40 dB (night,outside) are harmful to health.” At levels over 40dB, “Adverse health effects are observed,” and “many people have to adapt their lives to cope with the noise at night. Vulnerable groups are more severely affected.”
The 184-page report offers a comprehensive overview of research into the various effects of noise on sleep quality and health (including the health effects of non-waking sleep arousal), and is recommended reading for anyone working with noise issues. The use of an outdoor noise standard is in part designed to acknowledge that people do like to leave windows open when sleeping, though the year-long average may be difficult to obtain (it would require longer-term sound monitoring than is usually budgeted for by either industry or neighborhood groups).
While recommending the use of the average level, the report notes that some instantaneous effect occur in relation to specific maximum noise levels, but that the health effects of these “cannot be easily established.”