system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does it seem like people from the 40s/50s had distinctly different voices than people today?

Is it a matter of a slightly different accent? Is it a matter of recording quality? A mix of both?

People today can imitate the "voice styles" of people from these times, but nobody seems to just straight up have those kinds of voices. Why is that? Am I thinking too hard about it?
gpt
Accents change noticeably over fairly short periods. Before we developed the ability to record voices, this wasn't so obvious. Now that we can, accent shifts have become a subject of serious study.  It's not just the US, either - someone is going to come in here and insist that it's just a mid Atlantic accent, which isn't as common today as it used to be, but that doesn't really explain it. For one thing, Canadian film from back then also displays a significant accent shift, and is pretty noticeable when we hear it. Brits notice the same thing (it is really obvious comparing the queen today to her own speech 50 years back, incidentally). And even among US speakers, there's just as noticeable a difference among those who aren't using anything like a Mid-Atlantic accent at all. 

[tl;dr] accents have been changing all the time, but audio recordings forced us to notice it.