The general rule for Spanish pronunciation is that, barring an accent, words that end with vowels have stresses placed on the second-to-last syllable. However, with adverbs, there seem to be exceptions.
Take frecuentemente. It ends with a vowel, so it appears that the stress should go on MEN. But many dictionaries have spoken examples demonstrating that the stress is on CUEN. I could accept this if it had an accent, but it does not.
And none of these have accents. It is worth noting that Google's machine recording pronounces extremadamente as ex-tre-ma-da-MEN-te (likely because it has been programmed with the rule mentioned above), but Google's human voiceover for the word pronounces it as ex-tre-MA-da-men-te.
Are -mente adverbs exceptions to the pronunciation rules in casual/modern-day speech, or are the voiceovers for these dictionaries pronouncing the words incorrectly?