Eli5: Why do earplugs max out at 33db of noise cancelling?

Question

Eli5: Why do earplugs max out at 33db of noise cancelling?

In: 3288

Answer 1

If you block 100% of noise going into the ear, you’ll still hear at about -40db (to -60db depending on frequency) from conduction through your skull/bones instead, so that sets the absolute lower limit for blocking noise.

Also db is log not linear, and -30db is already about 1000:1 (99.9%) blocking so that is already pretty amazing.