Testing theories of vowel inherent spectral change

Abstract

Models which include information about vowel inherent spectral change (VISC) have higher correct classification rates, and greater correlation with human response patterns, compared to models which only include static spectral information. Three hypotheses have been proposed as to the aspect of VISC which is relevant for human perception. All three agree that the initial target (e.g., F1 and F2 values at the beginning of the vowel) is important. The dual-target hypothesis states that the final target (e.g., F1 and F2 values at the end of the vowel) is the other relevant factor. The target-plus-slope hypothesis states that it is the rate of change in spectral values over time that is relevant. The target-plus-direction hypothesis states that only the direction of formant movement (e.g., in an F1–F2 plane) is relevant. Synthetic /e/−/I /−/ε/ stimuli with a fixed initial target but varying final target, slope, direction, and duration were identified by monolingual Western Canadian English listeners. Models of the listeners perception were parametrized according to the three hypotheses. Results indicate that the final−target model outperformed the slope modal. Neither the linear−final−target model nor the direction model clearly outperformed the other, but a final−target model including a cubic term was superior.