Characterization of speech understanding in various types of noise.

This study examined (1) the effects of noise on speech understanding and (2) whether performance in real-life noises could be predicted based on performance in steady-state speech-spectrum-shaped noise. The noise conditions included a steady-state speech-spectrum-shaped noise and six types of real-life noise. Thirty normal-hearing adults were tested using sentence materials from the Cantonese Hearing In Noise Test (CHINT). To achieve the first aim, the performance-intensity function slopes in these noise conditions were estimated and compared. Variations in performance-intensity function slopes were attributed to differences in the amount of amplitude fluctuations and the presence of competing background speech. How well the data obtained in real-life noises fit the performance-intensity functions obtained in steady-state speech-spectrum-shaped noises was examined for the second aim of the study. Four out of six types of noise yielded performance-intensity function slopes similar to that in steady-state speech-spectrum-shaped noise. After accounting for individual differences in sentence reception threshold (SRT) and the offset between the signal-to-noise ratio for 50% intelligibility across different types of noise, performance in steady-state speech-spectrum-shaped noise was found to predict well the performance in most of the real-life noise conditions.