(PP314) Speech Intelligibility Gain in Reverberation for Elders with Binaural Losses with Amplification

With advanced amplification technology people still struggle to comprehend speech in noise (Prosser et al., 2009) and reverberation (Nabelek & Pickett, 1974). It was found that speech intelligibility improved when spatially separate noise from speech for listeners with normal hearing (NH), but this benefit was negatively impacted by age, hearing loss (HL), and reverberation (Marrone et al., 2008). This improvement is called speech intelligibility gain (SIG) comparing signal-to-noise-ratio (SNR) where speech and noise spatially separated to being presented co-located. However, no study has investigated hearing aid (HA) users’ speech perception involving reverberation and spatial separation of signal and noise. The purpose of this study was to determine the effects of reverberation on SIG for elders with binaural amplification to target 50% speech intelligibility.

Elders (60&+ yrs) with NH, mild-, moderate-, moderately-severe-, and severe-SNHL were recruited. Participants with HL were fit with Phonak Audeo 90M-RT binaurally and verified through a real-ear-measurement system. All participants completed a SIG test (developed from Koehnke & Besing, 1996) listening to stimuli presented via circumaural earphones and repeating the words heard. The phonetically balanced monosyllabic words (Egan, 1948) were presented at most comfortable level from 0º azimuth. Speech-spectrum noise was presented at 0º, +90º, or -90º azimuth; the level was varied adaptively (one-down/up procedure) to determine the SNR needed for 50% intelligibility. All subjects completed the SIG in anechoic (AN) and reverberant environments (RT₆₀ of 0.2s, 0.4s, 0.6s and 0.9s) at three noise locations. Listening conditions were tested in random order, at least twice for consistency, and words were selected randomly without replacement.

Data were analyzed using multivariate analysis and post-hoc test. Results revealed that SNR increased as RT increased for three noise locations and all groups. Higher SNR means greater difficulty to achieve the same intelligibility. The significant change in SNR (p< .05) occurred at RT0.4 and/or RT0.9 for NH-moderate-, and severe-group, at RT0.9 or no significant difference for moderately-severe group for noise center/left condition. SNR decreased when speech and noise spatially separated for all environments in all groups, but no change of SNR at higher RTs for moderate-severe-groups. The significant change in SNR (p< .05) due to noise location change occurred in AN for NH- and moderate-HL groups only. SNR increases with HL for all conditions, but the HL effects were diminished with HAs. SNRs were significantly lower (p< .0001) for NH & mild groups than other HL groups, but no significant difference between NH and mild-HL and among more severe-HL groups, confirming the aided benefit. In addition, SIG decreased with increasing RT from anechoic to RT0.4/0.6 for all groups, increased as RT increased for all groups at RT0.4/0.6-RT0.9, although no SIG for severe group at RT0.6-0.9 conditions. SIG was similar for all groups in most conditions further confirming the ability of using binaural cues with HAs.
The findings of this study may extend our understanding of binaural processing ability of binaural HA users in real-life situations, and hence help audiologists consulting patients to develop better communication or rehabilitation strategies in adverse listening environments.