US mines with the most noise samples over the legal limit

MSHA reports each noise sample as a dose against the allowance, so a dose over 100% is over the limit. It is not a decibel reading.

A sample over the PEL is an exposure measurement, not a violation and not a compliance judgment. It is also a measurement of the workplace, not of what reached the miner's ear: hearing conservation programs and the hearing protection worn during the shift are recorded separately in MSHA's data and are not reflected in these figures.

In practice this is a coal ranking. Of the 275,526 noise samples MSHA has published since 2000, 478 come from metal and nonmetal mines, spread across 11 of them. Those operations are covered by the same noise standard but are almost never sampled under it, so their absence reflects MSHA's sampling program rather than quiet worksites.

Only mines with at least 30 noise samples on record are ranked below, so a handful of readings cannot drive the rate.