Nighthawk,
Some (very) loud music has not in the least the detrimental effect as continious noise on flightdeck. Fact.
A continuous sound level of 80 dB or more will, in the end, cause hearing loss. Fact.
The noise level in B767 flightdeck exceeds 90 dB on occasion and is over 85 dB most of the time. Fact.
ANR technology is working superbly to reduce continuous noise up to -15 dB. This will also result in a lower audio volume selection to hear ATC or crewmembers. Fact.
KLM has abandoned ANR headsets introduction because of cost considerations. Even a pilot's own ANR headset may not be worn in KLM aircraft. Fact.
SJ