(100% OT of linked article: "a historic", not "an historic", unless you pronounce the word "istoric".)
https://en.oxforddictionaries.com/usage/a-historic-event-or-...
https://en.oxforddictionaries.com/usage/a-historic-event-or-...
Which we do (in Britain and the rest of the English speaking world outside North America), so "an historic" it is.
e.g. from BBC:
"An hour" on the other hand makes more sense, as that is truly a soft H.
History: /ˈhist(ə)rē/
Historic: /hiˈstôrik/
The 'h' is stressed in 'history', not in 'historic'. Try pronouncing 'historic' with a stress on the first syllable, it sounds wrong. Since it's softer in historic it's more natural (to me anyway) to use 'an'.
(Also, I'm french so I barely pronounce h's to begin with - so in my speech the stressed 'h' in history is kinda soft, and the unstressed h in historic is barely there.)
(edited)
$ ./anorack test_file
$ out:1: an historic -> a historic /hIst'0rIk/
Interesting. What if...
$ ...hacks phonetics.py to use "en-us" voice...
$ ./anorack test_file
$ out:1: an historic -> a historic /hIst'0rIk/
Hum... same result. What about:
$ ...hacks phonetics.py to use "en-wm" voice...
$ ./anorack test_file
$
Ah, finally someone gets it right :)
(just having a bit of fun, this is a cool work!)
Edit: formatting...
No need to feel ignorant; it's a nonstandard, eSpeak-specific notation.
$ espeak --voices | grep ' en-'
2 en-gb M english en (en-uk 2)(en 2)
5 en-sc M en-scottish other/en-sc (en 4)
5 en-uk-north M english-north other/en-n (en-uk 3)(en 5)
5 en-uk-rp M english_rp other/en-rp (en-uk 4)(en 5)
5 en-uk-wmids M english_wmids other/en-wm (en-uk 9)(en 9)
2 en-us M english-us en-us (en-r 5)(en 3)
5 en-wi M en-westindies other/en-wi (en-uk 4)(en 10)