Acoustic analysis of the effects of metrical regularity on interval durations

This paper presents a preliminary analysis of acoustic data collected in a magnetoencephalographic investigation of the effects of metrical pattern regularity on the subvocal rehearsal and production of speech.

Many languages exhibit a distinction between stressed and unstressed syllables. Stressed syllables tend to be more acoustically prominent than unstressed ones, exhibiting increased duration, acoustic intensity, and pitch range. Furthermore, utterances can be characterized with regard to their degree of metrical regularity, i.e. the extent to which they exhibit a consistent pattern of alternation between stressed and unstressed syllables.

The current study aims to investigate the effects of metrical regularity on the subvocal rehearsal and production of nonword sequences.

• Analyses of acoustic durations in spoken responses show that speakers adjust the timing of wore onsets in order to isochronize intervals between stressed syllables in irregular patterns.
• Analyses of acoustic energy envelopes show that regular metrical patterns exhibit periodic oscillatory variation on two timescales, one associated with words, the other with all syllables.

Moreover, the phase-offsets of word-level oscillations depend on the stress patterns of the words, and differences in phase are associated with differences in metrical structure. This latter finding provides the basis for subsequently planned analyses of magnetoencephalography (MEG) signal oscillations during subvocal rehearsal of metrical patterns.