What NRR do I actually need for concerts?

Most concert and festival reviewers across the sources we read recommend 15-20 dB of reduction so the music stays clear but safe. Loop Experience 2 (17 dB) is the most cited at this level. Anything in the 30+ dB range (foam) over-attenuates and muddies the music, which is why musicians and live-event reviewers generally avoid foam for concerts even though foam blocks more noise.