How can you tell if a syllable is unstressed or stressed?
I never would have believed this could be a problem until I met a native English speaker who was training to teach English and who genuinely couldn't tell which syllable of 'chicken' was stressed. Even when we all said 'CHICK - en' to her and also 'chick - EN', she simply couldn't hear the difference. Try saying CHICK-en and chick-EN yourself. Can you tell which syllable SHOULD be stressed? If not, I don't know what to tell you ... What @Keno said about 'base' words is true up to a point. But what about PHO-tograph, pho-TOG-rapher, and photo-GRAPH-ical?
Well, in SOME languages there is a rule. In French yopu always emphasise the first syllable. In Polish and Esperanto you always emhasise the penultimate syllable In English, you have to memorise it or look it up somewhere.. and sometimes the emphasis determines the meaning of the word , like in "record"
Keno is right to a point, but it's the fact that a syllable is NOT stressed that makes a vowel shorter- and often turns it into an "uh" sound. For example- PHO-tuh-graph, phuh-TOG-rapher and "phot-uh-graph-uh-cuhl You could also look it up in the dictionary and see which syllable is marked for stress: beam'- ing.
A good cheat to tell if a syllable would be stressed or unstressed is to put more emphasis on the base word. (Here, that would be 'beam'). So you would say BEAMing instead of beamING. Words that have longer vowel sounds are stressed as well. (ea is longer than i).