Development of a corpus of Mandarin sentences in babble with homogeneity optimized via psychometric evaluation

Objective: To develop a corpus of sentences in babble noise that is suitable for Mandarin-speaking children. Two experiments were conducted with specific aims of (1) developing sentence material that is grammatically and semantically within the linguistic abilities of children; and (2) improving the efficiency of the test by equalizing the relative intelligibility of individual items in sentences. Design and Study sample: Sentences were extracted from spoken material of Chinese children aged between 4 and 5 years of age. The sentences were tested for intelligibility in a four-talker babble by 96 adult native speakers of Mandarin. Psychometric functions were generated, and used for adjusting signal-to-noise ratios of individual items by varying the level of the time-locked babble to equate intelligibility of the target speech. These adjusted stimuli were tested for intelligibility using a different group of 64 adult listeners. Results: The signal-to-noise ratio for 50% correct was not different before and after adjustments (- 6.1 dB and - 6.0 dB, respectively). However, there was a significant reduction in standard deviation from 2.3 dB before adjustment to 1.1 dB after adjustment (p < 0.05). Conclusions: The experiments established a corpus of Mandarin BKB-like sentences with four-talker babble as competing noise, in which the test items' homogeneity was optimized via psychometric evaluation (HOPE).