Baseline Fall, bf

The Baseline fall (bf) option in Hz determines one aspect of the dynamic fundamental frequency contour for a sentence. If the bf option is 0, the reference baseline fundamental frequency of a sentence begin and ends at 115 Hz. All rule-governed dynamic swings in f0 are computed with respect to the reference baseline.

Some speakers begin a sentence at a higher f0 and gradually fall as the sentence progresses. This falling baseline behavior can be simulated by setting the bf option to the desired fall in Hz. For example, setting the bf option to 20 Hz causes the f0 pattern for a sentence to begin at 125 Hz (115 Hz plus half of bf) and to fall at a rate of 16 Hz per second until it reaches 105 Hz (115 Hz minus half of bf). The baseline remains at this lower value until it is reset automatically before the beginning of the next full sentence (right after a period, question mark, or exclamation point). The rate of fall (16 Hz per second) is fixed, regardless of the extent of the fall.

Whenever you include a [ + ] syntactic symbol in the text to indicate the beginning of a paragraph, the baseline is automatically set to begin slightly higher for the first sentence of the paragraph. While baseline fall differs among the speakers, it is not a good cue for differentiating among them. As long as the fall is not excessive, its presence or absence is hardly noticeable.

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