How can I hear which syllable is considered stressed in a Russian word? And: how, exactly, should stress in Russian pronunciation be realised?
My problem
I realise that to stress a syllable is to emphasise it, but there are various ways to do that, such as duration, (musical) pitch, clarity and volume. When I listen to audio samples, it often sounds to me as though the stress is on the syllable before the one marked as stressed. I suspect that part of the problem may be that when people enunciate carefully they pronounce unstressed syllables more clearly than normal, but I do not think that that is the whole story.
(I should also be interested in how those of the above characteristics which do not determine stress in Russian are used, but that should probably be a separate question.)
Examples
To take some examples:
- In Forvo, the 2nd, 3rd and 4th pronunciations (by Vospi, luba1980 and Mariya) of спасибо and various pronunciations of она sound like this to me. It seems to me that in such cases the pre-stressed syllable is somewhat higher pitched and often marginally louder but shorter than the “stressed” syllable.
- In Wikimedia (used by Wiktionary), I hear the same thing in оно (with a very quiet “stressed” ‘о’), while in она both syllables sound equally loud, but the pre-stressed one is still pitched higher. In спасибо, all three syllables sound almost equally loud, with спа higher and marginally louder, си a little longer and бо very short.
Note that these remarks do not apply in all cases; in other examples (such as спасибо spoken by Alexander Nevzorov at Forvo, 5th) I hear the stressed syllable as higher and louder, making it seem stressed to me.
It seems relevant, as suggested by Anixx, to compare cases of homographs such as писáть (write) and пи́сать (urinate) (both at Forvo); some more are listed in German Wikipedia.
Sources consulted
I have looked through Russian Phonology in English Wikipedia, but not found an explanation, and my Russian is not yet good enough to consult Russian sources.
P.S.
I see that Russische Phonetik § Betonung (Russian Phonetics § Stress) and Wortbetonung in der russischen Sprache (Stress in Russian) in German Wikipedia give useful information, though I am not yet sure if it is adequate; perhaps, if it is, I shall get round to answering this question (if no one else has) on that basis and/or translating that material into English Wikipedia.
P.P.S.
Note that I am not mainly asking how to pronounce a word given where the stress is: what I want to know is how to hear the accent, because what I hear seems to disagree with what is written/printed/displayed, and so I want to know which features matter most (so pronunciation comes in a bit too). An answer by Vurux says one should realise it “by increasing loudness a bit and prolonging the length of the vowel just a little”, but my point is that sometimes the syllable before sounds louder to me.