Duration and Intensity as Physical Correlates of Linguistic Stress

Abstract

English contains many pairs of words, e.g., contract, subject, digest, in which a change of meaning (from noun to verb) is accompanied, in the practice of many speakers, by a change of strong stress from the first to the second syllable. Spectrograms of 6 such pairs, uttered by 12 American speakers, were made and the duration and intensity ratios of the sounds in each word were examined. These measurements showed that when the stress was shifted from the first to the second syllable the most marked variations took place in the relative duration and intensity of the “vowel” portions of the speech wave, while other parts of the wave remained remarkably constant in these respects. By means of the pattern playback equipment, test words were synthesized and recorded in which the duration and intensity ratios of the two vowels in each word were made to vary over the critical range. This material was arranged in suitable test form and a group of American listeners was asked to judge, for each test item, whether the noun or the verb form had been uttered. The data obtained show that there is a good correlation between the perception of stress and the vowel duration and vowel intensity ratios. They also show the uncertainty range along these two dimensions for each pair of words and indicate that, in stress perception, duration and intensity changes may compensate for each other.