I have mixed rock 'n' roll to acoustic gigs and when the call is for high volume I use professional ear protectors which lower the sound level without distorting the frequencies. Industrial ear protectors are designed to kill the harmful high frequencies.
As a bass player in my younger days, I can't say my hearing has not been damaged by standing too near the drummer's cymbals.
A good aid to a sound man is a Real Time Sound Analyser which gives a 1/3 octave graphic readout of the sound frequencies coming out of the mains.