The Benefits of Increased Sensation Level and Bandwidth for Spatial Release From Masking.
Kasey M Jakien, Sean D Kampel, Samuel Y Gordon and 1 others
PMID 27556520WHAT IT FOUND
Speech recognition thresholds improved when the target was at a higher level and when competing talkers were spatially separated.
When audibility was equated across frequencies, bandwidth also helped, but this was a lab study, not hearing aid fitting.
Key findings
01Speech recognition thresholds were better at the higher target level than at the lower target level, by 1.34 dB when maskers were colocated and 3.7 dB when maskers were spatially separated.
02Listeners performed best with spatially separated maskers at the higher target level and broadband filtering, and performed more poorly when separated maskers were low-pass filtered at the lower target level.
03Pure-tone average was a significant predictor of thresholds, while age was not.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used virtual spatialized sentences presented through earphones in a sound-attenuated booth, not hearing aids or real-world listening environments. Participants in experiment 1 had bilateral pure-tone averages below 37 dB hearing level, and participants in experiment 2 had thresholds of 70 dB hearing level or better at all octave frequencies between 250 and 8000 Hz, so the findings may not apply to people with more severe hearing loss. For the experiment 1 level comparison, only listeners who completed both the low and high target-level conditions were included, and the supplied text does not give the final analysed number for that comparison. Five listeners with pure-tone averages greater than 28 dB hearing level had reduced audibility in the high-frequency bands because band levels were capped at 70 dB sound pressure level. The participants had fairly symmetrical hearing at 2 kHz and below, so the results may not apply to people with asymmetric hearing loss. The authors state that it is difficult to determine from the data whether binaural cues or increased speech information caused the improvement. Age was not a significant predictor in either experiment, although the authors note that performance generally worsened as age increased.
Declared interests
The authors declare no conflicts of interest.
The easy way to misread this
Do not conclude that raising hearing aid gain will improve patients' everyday speech recognition. The study tested virtual spatialized speech through earphones, not hearing aids, and the authors state that it is difficult to determine whether binaural cues or increased speech information caused the improvement.