Safe exposure times vs. SPL
Duration per daySound level (dB, C weighted)
8 hr85
4 hr88
2 hr91
1 hr94
30 min97
15 min100
7 min 30 sec103
3 min 45 sec106
1 min 52 sec109
56 sec112
28 sec115
none> 115

Ref: NIOSH