Loudness, Its Definition, Measurment, and Calculation - Harvey Fletcher and W.A.Munson, Bell TelephoneLlaboratories - JASA October 1933

At your risk. The amazing paper publised nearly 100 years ago showing that loudness does not depend only on intensity but frequency, waveform, psychological state of listener etc. my humble observation while reading this paper is that while +70dB intensity compared to threshold at 1KHz can still not be heard by a human it may have dramatic psychological effect to a human being if coming say from machinery in the same building (structure born sound) for prolonged periods, (for example in the house you live in, try to sleep etc). After all sub or very low frequency audio is used in thriller movies. So local authaurities must take into account, a law on moise protection should take all these into account. If there is not data available then research is needed.