There's no hearing protector in the world rated at 75 dB. I think the maximum you can achieve is around 40 dB. Hearing protection isn't additive, so if you wear earmuffs with 30 dB NRR and earplugs with 30 dB NRR, you don't get 60 dB NRR, you're still close to around 30 dB NRR.