Loud sounds can harm our ears, especially if the noise appears all of a sudden. It's because the so-called acoustic reflex has not enough time to take effect.
A car manufacturer has studied this phenomenon because drivers got ear injuries after car accidents. How could it better protect them?
The solution is to emit a moderately loud sound in the car just before a crash, once the collision is considered to be inevitable. That way, ears protect themselves. Smart engineering!
The acoustic reflex features movements of the tensor tympani muscle. Today I learned that some people have the ability to control it and reduce the perception of ambient sounds by about 15dB. It's like noise cancelling headphones for free.
There's even a Reddit community for this: https://old.reddit.com/r/earrumblersassemble/