FREQUENCY IMPORTANCE FUNCTIONS FOR WORDS, SENTENCES, AND CONTINUOUS DISCOURSE

This research determined frequency importance functions (FIFs) for wor ds, sentences, and continuous discourse under comparable conditions so that contextual effects of speech could be isolated. A male talker re corded 616 monosyllabic words, 176 meaningful sentences, and 44 contin uous discourse (CD) passages. Twenty-four participants with normal hea ring made intelligibility estimates of the CD passages and sentences a nd identified words in each of 44 low- and high-pass filtering and sig nal-to-noise ratio conditions. Plots of frequency versus percent of co ntributed intelligibility, or the FIFs, revealed that the frequency ba nd that contributes the most to intelligibility is centered near 2000 Hz for all three types of speech. The results show a single peak in th e importance function and a statistical analysis of the shape of the F IF (with kurtosis the pertinent measure) shows that there is a signifi cant difference in the shape of the FIF based upon speech type. The da ta were also calculated into near-octave bands with similar results. T he statistical analysis presented provides the basis for a test of the hypothesis: The degree of context or message redundancy is related to the relative importance of the frequency bands. The findings potentia lly have clinical as well as predictive implications.