Levels...
The following permitted sound levels are published by American Occupational Safety & Health Administration as thresholds for safe “listening”:
hours a day intensity
8 90 dB
6 92 dB
4 95 dB
3 97 dB
2 100 dB
1.5 102 dB
1 105 dB
0.5 110 dB
0.25 or less 115 dB
Read it like “1 hour or more at an overcooked death metal concert can be dangerous for your health”. That is why firing a rifle again and again, at its 160dB blasts, for 3 minutes without any protective aid may not be a good idea.
We, audiophiles, do not need measuring devices to check whether or not we are over the limit – within the restricted area we have for our hobby- the listening the room- it is unlikely that we listen to our music at the levels exceeding 90dB. The sound waves especially at lower octaves develop differently from what they do in the large halls and open spaces, they mix with early reflections and reverberations, making music requiring less watts to play really loud and preventing us to go over the top. It is good to know that increasing the overall loudness at home by 3dB requires double the power of the preceding wattage – even though the perception is very small and for some almost unnoticeable.