Evaluation of the effect of stress on formants in Farsi vowels

Stress is known as an important prosodic property of speech. Recognition of stressed speech, due to the effects of stress on acoustic features of speech, has always been considered more difficult, in comparison to unstressed speech. On the other hand, preparing a large speech corpus to include all different possible occasions of stressed speech, for the purpose of training in speech recognition, is very difficult. This is true for any language and Farsi (Persian) is no exception. Due to the importance of formant frequencies, they have long been considered in the recognition task. In this paper, we report on our efforts to find out the potential effects of stress on the formant frequencies. The results of our statistical evaluations demonstrate changes in the formant frequencies in certain directions, due to stress, that may be found helpful in improving automatic recognition of stressed speech.