Bit of HUF
Loud high pitch noise is painful at best and you block your ears quickly, but sustained loud low pitched noise is not as painful but does more damage to hearing because of the energy and the time. Don't believe me, go take a ride in a mates car with a competition sound system. Ask them to play a lower note song, ie rnb hip hop, then get them to play something wil alot of highs, ie opera or jazz. You can sit in front of the stereo or in the car for longer periods of time with the lower notes (ie bassy songs) moreso than the High notes (ie Jazz, Classical or dare I say it, Deathmetal). I myself find that the Higher pitched notes hurt more and cause me to physically get out of the car/room, to get away from the music at a great rate of knots, whereas the lower notes I can listen to all day. Try another thing. Whisper something to them, thats barely audible. If they like RnB or Hiphop, read: bassy songs, they wont be able to hear you.
In aviation we are exposed to all types of low pitched noise ie Twin's that aren't synchronised, Exhaust note from essentially straight headers.
All it comes down to is Duration and Energy. Think of the duration of energy transfer as the current, and the pitch as the voltage. Low voltage + high current = instant death. Low Current + High Voltage = Pain but not death.
ANR is designed to stop the duration. It does this by lowering the exposure to the low pitch noise. Thats all its actually doing. Blocking lower pitch noise.
4 hours with a cockpit at 90dB or 4 hours in the cockpit with 65dB. I will take the 65dB any day