What's uncanny here is that having a goatee doesn't make you belong to any social group you could think of explicitly and enjoy belonging to. I guess the relationship is mostly driven by a mix of physionomical traits (gender + age) and the fact they correlate well to having a goatee (which isn't a tiny class anyway). Or there are indeed "deep" social structures to which we belong and are yet unable to identify.
[1] http://all-about-linguistics.group.shef.ac.uk/branches-of-li...
Edit: there may well be an immense data trove hidden in people's voice. That could be a very useful way to enrich datasets internally a bit like recommendation engines work: if my neighbour speaks like I do, then he must enjoy the same things as I.
Extreme example, compare audio at 4m and 21m - https://www.youtube.com/watch?v=6dbQ2OA4SRA
Clearly a different top end.
Did a little tinkering in Audacity and with the beard there's a standard roll off from 3khz to 10khz. Without there's a weird flat spot in the same area (both are averaged over 20 seconds or so)