You will most likely never hear any sound at -120 dBFS unless you’re in an anechoic chamber and even then the noise that your own body generates will probably dominate your auditory sense.
Thank you for that comment. I couldn’t agree more.
Curious at what point noise reduction could be considered "good enough".
For me personally; in a super quiet environment, I can hear around -100 dB S/NR, when using headphones. But for me, -80 dB S/NR is actually "good enough". "Good enough" probably also depends on your own personal auditory system, aka hearing. Any ringing in your ears? Also your listening space; while sitting in it, can you hear your refrigerator, air conditioner, forced air furnace, washing machine, dishwasher, neighbors, kids, etc.? If you can, that changes that -120 dB S/NR (down to possibly -70 dB or even higher - higher meaning more noise, as like maybe -60 dB) provided by your audio components. Although when discussing environment noise levels, those numbers are probably better represented in the SPL category.