If we discover a PBH in our outer solar system does that mean that Elon Musk could fly a rocket there and orbit for a while and return to Mars thousands of years in the future after it has already been colonized? That would be cool, for him.

I found a nice article that discusses the EU and OSHA regulations, as well as other useful information such as the decibel levels of common sounds.

The OSHA regulations in summary:
90 dbA 8 hrs
92 dbA 6 hrs
95 dbA 4 hrs
97 dbA 3 hrs
100 dbA 2 hrs
102 dbA 1.5 hrs
105 dbA 1 hr
110 dbA 0.5 hr
115 dbA 0.25 hr or less

They also refer to a study that looked at people's headphone settings in different environments. The study found that in a quiet room listeners set headphones volumes at an average of 69 dB. On a noisy street the average was 80 dB. In other words, for most people - this isn't anything to worry about even if you have a long daily commute. Just keep the volume level down.