Vulnerable groups cannot be protected sufficiently at this level.Therefore, IT should be considered only as a feasibility-based intermediate target which can be temporarily considered by policy-makers for exceptional local situations.An interim target (IT) of 55 d B L is recommended in the situations where the achievement of NNG is not feasible in the short run for various reasons.It should be emphasized that IT is not a health-based limit value by itself.
Even at very low levels, physiological reactions (increase in heart rate, body movements and arousals) can be reliably measured.
Above 55 d B, cardiovascular effects become the major public health concern, which are likely to be less dependent on the nature of the noise.
Closer examination of the precise impact will be necessary in the range between 40 d B and 55 d B as much will depend on the detailed circumstances of each case.
Below the level of 30 d B L , no effects on sleep are observed except for a slight increase in the frequency of body movements during sleep due to night noise.
There is no sufficient evidence that the biological effects observed at the level below 40 d B L is equivalent to the lowest observed adverse effect level (LOAEL) for night noise.