Relationship between Chinese speech intelligibility and speech transmission index under reproduced general room conditions

The subjective Chinese (Mandarin) articulation scores of a total of 50 sound conditions, namely at 12 receiver positions in four rooms, were obtained by expert listeners based on in-situ measured binaural room impulse responses (BRIRs) and binaural technology for headphone reproduction from a phonetically balanced test. The relationship between Chinese speech articulation scores and the speech transmission index (STI) according to IEC 60268-16 was established. The spectrum difference between the average spectrum of Chinese and that recommended by IEC may noticeably influence the measurement results with a STI difference of up to 0.054. However, the STI method can evaluate Chinese intelligibility without modulating the correction factor values recommended by IEC; the standard deviation between the articulation scores and the curve was 5.70%, which is relatively small.