Effect of F0 contour on perception of Mandarin Chinese speech against masking

Abstract

Intonation has many perceptually significant functions in language that contribute to speech recognition. This study aims to investigate whether intonation cues affect the unmasking of Mandarin Chinese speech in the presence of interfering sounds. Specifically, intelligibility of multi-tone Mandarin Chinese sentences with maskers consisting of either two-talker speech or steady-state noise was measured in three (flattened, typical, and exaggerated) intonation conditions. Different from most of the previous studies, the present study only manipulate and modify the intonation information but preserve tone information. The results showed that recognition of the final keywords in multi-tone Mandarin Chinese sentences was much better under the original F0 contour condition than the decreased F0 contour or exaggerated F0 contour conditions whenever there was a noise or speech masker, and an exaggerated F0 contour reduced the intelligibility of Mandarin Chinese more under the speech masker condition than that under the noise masker condition. These results suggested that speech in a tone language (Mandarin Chinese) is harder to understand when the intonation is unnatural, even if the tone information is preserved, and an unnatural intonation contour decreases releasing Mandarin Chinese speech from masking, especially in a multi-person talking environment.

Fig 1. Average hearing thresholds in the left ear (filled circles) and right ear (open circles).

ANSI: American National Standards Institute (S3.6–1989). Error bars represent the standard errors of the mean.

Fig 2

Sketch map of an example of a target sentence with its intonation pattern (left top panel) and three types of intonation: (1) flattened intonation conditions (top-right panel), (2) typical intonation conditions (bottom-left panel), and (3) exaggerated intonation conditions (bottom-right panel).

Fig 3

Group-mean percent-correct syllable identification for the last target keyword as a function of the signal-to-masker ratio (SNR) for younger (top panels) and older (bottom panels) participants when the masker was noise (left panels) or speech (right panels) under each of the intonation conditions: (1) flattened intonation conditions (open circles), (2) typical intonation conditions (filled circles), and (3) exaggerated intonation conditions (filled squares). Group-mean best-fitting psychometric function curves for the last keyword are shown in each of the panels.

Fig 4. Group-mean threshold (μ) values for recognizing the final target keyword for each intonation condition when the masker was either noise or speech.

Error bars indicate the standard errors of the mean. **: the difference was significant.