When focussing on tasks, the human brain filters out signals it decides
are extraneous to the task on hand. This is what causes many vehicle
accidents where people fail to see objects. They are seen, but not
processed in higher areas of the brain.

Exactly the same can happen with audible warnings - they are heard but
not processed.

I had a glider colleague who was famous for gear-up landings and who
had the loudest and most obnoxious gear warning klaxon installed. One
day, we saw him descending on final with the warning blaring, clearly
audible from a hundred yards away. He then proceeded to land gear up,
as usual.

I prefer check lists, but must note I have seen another colleague
return from a flight with gear extended then retract it on final as he
went through his pre-landing checks!

I have yet to land gear up but presume it could happen if I am
distracted or in a hurry.

Mike