Construction and evaluation of the Mandarin Chinese matrix (CMNmatrix) sentence test for the assessment of speech recognition in noise

Abstract

Objective: Development of the Mandarin Chinese matrix (CMNmatrix) sentence test for speech intelligibility measurements in noise according to the international standard procedure.

Design: A 50-word base matrix representing the distribution of phonemes and lexical tones of spoken Mandarin was established. Hundred sentences capturing all the co-articulations of two consecutive words were recorded. Word-specific speech recognition functions, speech reception thresholds (SRT: signal-to-noise ratio (SNR), that provides 50% speech intelligibility) and slopes were obtained from measurements at fixed SNRs. The speech material was homogenised in intelligibility by applying level corrections up to ± 2 dB. Subsequently, the CMNmatrix test was evaluated, the comparability of test lists was measured at two fixed SNRs. To investigate the training effect and establish the reference data, speech recognition was measured adaptively.

Study sample: Overall, the study sample contained 80 normal-hearing native Mandarin-speaking listeners.

Results: Multi-centre evaluation measurements confirmed that test lists are equivalent in intelligibility, with a mean SRT of −10.1 ± 0.1 dB SNR and a slope of 13.1 ± 0.9 %/dB. The reference SRT is −9.3 ± 0.8 and −11.2 ± 1.2 dB SNR for the open- and closed-set response format, respectively.

Conclusion: The CMNmatrix test is suitable for accurate and internationally comparable speech recognition measurements in noise.

Keywords:

• Chinese speech test
• speech reception threshold (SRT)
• Mandarin sentence test in noise
• matrix test

Acknowledgements

The authors thank the talker Yuyao Sun for her excellent contribution as well as Lin Li and Guoping Li for their support with the compilation of test material, Jingyu Yang, Meihong Wang, Yuexi Liu, Xiaoying Bian and MinNey Wong for helping with the data collection and all the participants.

Declaration of interest

No potential conflict of interest was reported by the authors.

Notes

1 Named according to ISO Language Name (ISO 639-3), where the ISO Language Code for Mandarin Chinese is CMN.

2 Note that syllables and phonemes are presented in Pinyin, the official Romanization system of standard Chinese, throughout the paper.

3 The difference between mean and median slope was due to some extremely steep slope estimates.

4 The non-native listeners are very experienced in the development of speech test materials and extended the judgements of the native listeners with a focus on possible acoustical artefacts that could influence the naturalness of sound impression.

5 For example, the word “keep” is pronounced “liú Xià” in Mandarin Chinese, whereas in some regions of Anhui province, it is pronounced “liú Hà”. When it comes to the northern regions of Hebei province, which is a 100 Km away from Anhui province, the pronunciation would be “Liù Xiǎ“. However, despite of the great differences in the pronunciation of the same word, the listeners from these two regions could easily and correctly recognise the word “liú Xià” in Mandarin Chinese.

Additional information

Funding

This work was supported by European Union project “Innovationsverbunds für integrierte, binaurale Hörsystemtechnik (VIBhear)” in the Europäischer Fonds für regionale Entwicklung (EFRE) and by Cluster of Excellence “Hearing4all” (EXC 1077/1) in the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG). The study performed in Hongkong was partly supported by Sivantos Pte Ltd and in Beijing was partly supported by Chinese National Science Foundation of China (NSFC, project number 81460099).