Difference limens for fundamental frequency contours in sentence level stimuli

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Abstract
Two experiments were performed to measure the difference limen (DL) for fundamental frequency using sentence level speech stimuli. In experiment I a male reader recorded five sentences. They were analyzed and synthesized using a linear prediction vocoding system. Part of each sentence was varied in 5‐Hz steps above and below the original contour. Sentences (original contour and one of the changed contours) were presented to listeners using the method of constant stimuli. DL's ranged from less than 5 to 15 Hz depending on the sentence. There was no significant difference between DL's as a function of direction of change (up or down from original). Experiment II was an attempt to determine if the variability in DL due to sentences was a function of differences in placement of the frequency change. The changes in fundamental frequency began and ended at voiceless portions in all sentences. The median DL for the speaker also used in experiment I was 12 Hz. No significant differences as a function of sentences were found. For another speaker the DL's were over 15 Hz.