After a quick internet search I found this
https://www.space.com/17307-neil-arm...tep-quote.html
which discusses the did he / didn't he say "a man".
Basically listeners at the time did NOT hear the "a", but Armstrong insisted he said it.
Later (2006) computer analysis of the track "found evidence that the missing "a" had been spoken after all: It was a 35-millisecond-long bump of sound between "for" and "man" that would have been too brief for human ears to hear."
What is not clear from that article is whether NASA later "enhanced" the unheard "a"
Peter