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

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.