The role of stress accent in the understanding of sentences in noise

Abstract

When a target sentence is presented in noise, the stressed syllables therein will constitute epochs with a high likelihood of S/N increase. Since in spontaneous speech stressed syllables have significantly higher information content than unstressed syllables [S. Greenberg et al., in Proc. 2d Intern. Conf. Human Lang. Technol. Res. (2002), pp. 36–43], it follows that masking the stressed syllables will negatively impact the perception of neighboring unstressed syllables. This hypothesis was tested by varying the S/N of only the stressed syllables in sentences embedded in otherwise unmodulated speech-spectrum noise. Results suggest that, compared to conditions with absent or decreased-S/N stressed syllables, increasing the S/N during stressed syllables increases intelligibility of the unstressed syllable or syllables that follow. Since the unstressed syllables are rarely masked in the classic, energetic sense, the phenomenon reported constitutes an instance of informational masking. The masking can affect perception at the phonemic as well as on higher linguistic levels, depending on the information provided by sentence context.