(PP108) Spatial Separation of Speech and Noise Benefit in Reverberation for Elders with Mild to Severe Loss

The ability to understand speech can be degraded by noise, reverberation (Helfer & Wilber, 1990), and aging (Wong et al., 2010), and this difficulty is exacerbated when accompanied by hearing loss (HL) (Fogerty et al., 2015). However, when competing noise comes from a different location than speech, listeners experience a benefit in comprehension of speech, but less benefit for elders, especially with HL (Dubno et al., 2002). Marrone et al. (2008) found reverberation negatively affects the benefit of spatial separation on speech recognition with two short reverberation times (RTs). It is not clear the systematic impact of reverberation and HL on spatial separation of speech and noise benefit. This study included more RTs and different degrees of HL to investigate how reverberation and HL affect the spatial separation benefit for elders.

Five group (normal hearing (NH), mild-, moderate-, moderately-severe-, and severe-SNHL) unaided elders (60&+ yrs) completed a virtual speech intelligibility gain (SIG) test (developed from Koehnke & Besing, 1996) listening to stimuli presented via circumaural earphones and repeating the words heard. The stimuli, 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 one-up procedure) to determine the signal-to-noise ratio (SNR) needed for 50% intelligibility. All subjects completed the SIG in anechoic 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 Tukey Honestly Significant Difference test. Results revealed listeners with HL had significantly higher SNR than those with NH (p< .0001), and SNR increased with increasing HL for all conditions, but no significant difference between moderate and moderately-severe groups. Higher SNR means greater difficulty to achieve the same intelligibility. SNR increased as RT increased for three noise locations and all groups. The significant change in SNR (p< .0001) occurred at RT0.4 for all noise locations and all groups, with exceptions of significant change at RT0.2 for moderate noise right and no significant difference for severe group noise center. SNR decreased when speech and noise spatially separated for all environments in all groups, with exceptions of no change of SNR at higher RTs (RT0.6/0.9) for moderate to severe groups. The significant change in SNR (p< .0001) due to noise location change occurred in AN and/or RT0.2/0.4 for all groups. In addition, intelligibility benefit increased with HL and decreased with increasing RT for shorter RTs and less HLs. Reverberation smears binaural timing cues therefore may decrease spatial separation benefit. Listeners with HL had higher SNR when signals co-located, but SNR decreased with spatial separation, further confirming the fact of release of masking and the ability to use binaural cues for listeners with HL.
The clear effect of increasing reverberation and HL on speech intelligibility provides audiologists useful information in consulting patients to develop better communication or rehabilitation strategies in adverse listening environments.