Fundamental frequency as basis for speech segmentation modeling

The present study investigates the relevance of fundamental frequency in speech segmentation models intended to simulate infants. Speech from three different conditions (infant-directed speech to 3and 12-month-olds, and adult-directed speech) was segmented based on fundamental frequency information, using a variant of the dpn-gram segmenting technique (highlighting similar segments as lexical candidates). The spectral distance between segments that were found based on fundamental frequency similarity was calculated, and compared to the spectral distance between segments that were found using transcription as basis for segmentation, as well as to the spectral distance between randomly paired segments from the same speech materials. The results show the greatest within-condition difference in speech directed to 3-month-olds, in which segmenting based on fundamental frequency similarity generated segment pairs with smaller spectral distance than did transcription-based segmentation or random segment pairs. Speech directed to 12-month-olds resulted in a somewhat smaller difference when using fundamental frequency data compared to when using transcriptions. For adult-directed speech, no difference was found in spectral distance between pairs generated by the different bases for segmentation. Neither segmenting speech by highlighting similar segments as lexical candidates, nor using fundamental frequency as basis for segmentation is optimal for a speech segmentation model intended to simulate 12-montholds or adults. These groups are more likely to segment speech based on their already present or growing linguistic experience than on acoustic similarity only. However, for a model simulating a 3-month-old infant, the present segmentation procedure and its basis for segmentation are more plausible. When modeling speech segmentation in an infant-like manner it is important to take into account both that the cognitive abilities of infants develop rapidly during the first year of life, and that some aspects of their linguistic environment vary during this period.