Performance of an expert spectrogram reader. II

Analysis of the videotaped performance of an expert spectrogram reader revealed the control strategy and sources of knowledge used by the expert while reading spectrograms. Spectrograms were read in two stages: segmentation and labeling. During segmentation, which was usually performed in a single pass from left to right, segment markers were placed on the spectrogram to indicate roughly phone-sized units. Segmentation was accomplished through the detection of spectral discontinuities, although the precise placement of segment markers was guided by a detailed knowledge of acoustic phonetics. Labeling was not performed left to fight, and was usually guided by an “easiest segments first” strategy. The vast majority of segments were identified through the recognition of characteristic patterns and salient features. The identification of other segments required the application of knowledge about coarticulation and phonological rules. Several experiments revealed that the expert did not use higher-order knowledge (e.g., lexical, syntactic, or semantic) during labeling—performance was slightly better on nonsense utterances than English sentences. Implications of the expert's performance will be discussed for theories of speech perception, machine recognition of speech, and the development of aids for the speech- and hearing-impaired.