How did where someone was sitting affect their availability to respond? I ask because I have a very old memory of reading that anything more than 70 walking pa

How did where someone was sitting affect their availability to respond? I ask because I have a very old memory of reading that anything more than 70 walking paces away was a phone call or an email. I've seen that distant shrink over the years and I have seen people wuse electronic communication if someone is 3 ft away. I could think of several causes for unavailability but I'm not going to speculate when you can simply answer.