Speech Intelligibility and Recall of Spoken Material Heard at Different Signal-to-noise Ratios and the Role Played by Working Memory Capacity

We studied speech intelligibility and memory performance for speech material heard under different signal-to-noise (S/N) ratios. Pre-experimental measures of working memory capacity (WMC) were taken to explore individual susceptibility to the disruptive effects of noise. Thirty-five participants first completed a WMC-operation span task in quiet and later listened to spoken word lists containing 11 one-syllable phonetically balanced words presented at four different S/N ratios (+12, +9, +6, and +3). Participants repeated each word aloud immediately after its presentation, to establish speech intelligibility and later on performed a free recall task for those words. The speech intelligibility function decreased linearly with increasing S/N levels for both the high-WMC and low-WMC groups. However, only the low-WMC group had decreasing memory performance with increasing S/N levels. The memory of the high-WMC individuals was not affected by increased S/N levels. Our results suggest that individual differences in WMC counteract some of the negative effects of speech noise. Copyright (c) 2012 John Wiley & Sons, Ltd.