nope, i could always react fast enough, the stairs in my parents house were pretty noisy.
But my brother once walked in when i was having sex, great reaction, he hastly shut the door waited 3 seconds, knocked and said "i am entering now". Had no lock on my door because he had to go through my room to get to his. It wasnt a big deal, i never had the feeling of it being something shameful. You lose that pretty quickly when you had a few conversations with people that are having sex at the same time.
But my brother once walked in when i was having sex, great reaction, he hastly shut the door waited 3 seconds, knocked and said "i am entering now". Had no lock on my door because he had to go through my room to get to his. It wasnt a big deal, i never had the feeling of it being something shameful. You lose that pretty quickly when you had a few conversations with people that are having sex at the same time.