Great question. It is a reflex action and triggered by loud noise. There is a very brief delay therefore abrupt loud sounds may not be dampened, such as a gunshot. We don’t notice it except with continuous loud noise it will seem less if the noise continues. It can only do so much to protect from hearing loss. Anything under 80 dB will probably not trigger it. If your ears ring after loud sounds the reflex mechanism was overloaded and could not dampen the loudness to prevent damage. This is how I discovered that adjusting the volume while listening showed me that at times it was too loud. Sometimes what you love will hurt you! Be kind to yourselves.
Real time sound levels
This is a follow up to a previous post concerning hearing damage from excessive sound levels. I have discovered that by adjusting the spl of the music you’re listening to in real time you can keep it under 80 dB or even 75dB. Use your remote volume control. Your ears adjust to the lower level. If you limit the high decibels there is no reflex contraction of the stapedius muscle to dampen the stapedius bone to try to limit damage to the cochlea from excessive sound levels. I use NIOSH to measure spl. I enjoy the music as much and will for a longer time. I found that I was routinely listening to music at levels higher than 80 dB. Some damage has already been done but I’m trying to limit further damage.