Acoustic correlates of form class

A number of recent experimental studies have begun to demonstrate the importance of lexical stress cues for segmentation and syllabification strategies (e.g., Treiman, 1989;Cutler, 1991). Stress information also plays a key role in many recent theories of phonological structure both at lexical (Chomsky and Halle, 1968; Hayes, 1981; Libermanand Prince, 1977) and sentential levels (Beckman, 1986; Pierrehumbert, 1980). These studies convincingly argue that lexical stress information is crucial for the processing of continuous speech.

Four relevant acoustic parameters have been identified as possible cues to lexical stress.The present research uses these acoustic cues to investigate grammatical class differences in English. The question addressed is whether there are any systematic acoustic differences that can distinguish grammatical classes (i.e., nouns and verbs) in English.

Beginning in the 1950's, a number of studies investigated the acoustic correlates of lexical stress in a variety of languages including English, Polish, French, and Swedish (for reviews, see Gay, 1978; Lehiste, 1970). These studies concentrated on four acoustic measures of perceived stress: duration, intensity, fundamental frequency, and spectral composition.

In general, longer duration, greater amplitude, higher fundamental frequency, and less vowel reduction in a syllable contribute to the perception of stress (Bolinger, 1958; Fry, 1955, 1958; Lieberman, 1960; Lindblom, 1963). However, the individual contribution of each of these factors in signaling lexical stress remains unclear. While some studies find that fundamental frequency appears to be the most predominant cue to perceived stress, variations in duration, amplitude and formant structure also systematically contribute to stress judgments.

Moreover, the relative importance of each of these parameters varies with the position of the lexical item in the sentence, suggesting a number of interactions (Morton and Jassem, 1965; Gay, 1978; Nakatani and Aston, 1978) In speech production, then, a complex of acoustic cues, including fundamental frequency, duration, intensity, and spectral composition, appears to collectively contribute to the perception of contrastive stress.